Pro-democracy activist Leung Kwok-hung, also known as 'Long Hair', shouts slogans during a protest on anniversary of the death of Nobel Peace Prize-winning dissident Liu Xiaobo, in Hong Kong, China July 13, 2020. REUTERS/Tyrone Siu 

Liu Xia, Chinese artist, poet, and the widow of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo, takes part in a panel discussion held at Bohemian National Hall, Columbia University, in Manhattan, New York, U.S., September 26, 2018. REUTERS/Amr Alfiky 

Liu Xia (R), Chinese artist, poet, and the widow of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo, and Chinese author Liao Yiwu (C) take part in a panel discussion held at Bohemian National Hall, Columbia University, in Manhattan, New York, U.S., September 26, 2018. REUTERS/Amr Alfiky 

Liu Xia, Chinese artist, poet, and the widow of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo, takes part in a panel discussion held at Bohemian National Hall, Columbia University, in Manhattan, New York, U.S., September 26, 2018. REUTERS/Amr Alfiky 

Liu Xia, Chinese artist, poet, and the widow of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo, takes part in a panel discussion held at Bohemian National Hall, Columbia University, in Manhattan, New York, U.S., September 26, 2018. REUTERS/Amr Alfiky 

Journalist Ian Johnson speaks during a memorial event to mark the first anniversary of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo's death at Gethsemane church in Berlin, Germany, July 13, 2018. The photo in the background shows Liu Xiaobo with his wife Liu Xia. REUTERS/Fabrizio Bensch 

German singer and former dissident Wolf Biermann performs during a memorial event to mark the first anniversary of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo's death at Gethsemane church in Berlin, Germany, July 13, 2018. The photo in the background shows Liu Xiaobo with his wife Liu Xia. REUTERS/Fabrizio Bensch 

German singer and former dissident Wolf Biermann performs during a memorial event to mark the first anniversary of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo's death at Gethsemane church in Berlin, Germany, July 13, 2018. REUTERS/Fabrizio Bensch 

German singer and former dissident Wolf Biermann attends a memorial event to mark the first anniversary of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo's death at Gethsemane church in Berlin, Germany, July 13, 2018. REUTERS/Fabrizio Bensch 

People attend a memorial event to mark the first anniversary of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo's death at Gethsemane church in Berlin, Germany, July 13, 2018. REUTERS/Fabrizio Bensch 

Former German President Joachim Gauck and his partner Daniela Schadt attend a memorial event to mark the first anniversary of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo's death at Gethsemane church in Berlin, Germany, July 13, 2018. REUTERS/Fabrizio Bensch 

People attend a memorial event to mark the first anniversary of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo's death at Gethsemane church in Berlin, Germany, July 13, 2018. REUTERS/Fabrizio Bensch 

A statue of Nobel Peace Prize-winning dissident Liu Xiaobo is seen during a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

A statue of Nobel Peace Prize-winning dissident Liu Xiaobo is seen during a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

Raindrop are seen on a statue of Nobel Peace Prize-winning dissident Liu Xiaobo during a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

Supporters of Nobel Peace Prize-winning dissident Liu Xiaobo pay tribute in front of his statue during a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

Supporters of Nobel Peace Prize-winning dissident Liu Xiaobo pay tribute in front of a his statue during a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

Supporters of Nobel Peace Prize-winning dissident Liu Xiaobo lay flowers in front of his statue during a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

Supporters of Nobel Peace Prize-winning dissident Liu Xiaobo take part in a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

The shadow of a supporter is cast on a backdrop as he pays tribute during a candlelight vigil to mark the first anniversary of the death of Nobel Peace Prize-winning dissident Liu Xiaobo, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

A man, wearing a T-shirt with a portrait of Nobel Peace Prize-winning dissident Liu Xiaobo, joins a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

A statue of Nobel Peace Prize-winning dissident Liu Xiaobo is displayed in front of his portrait, during a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

Supporters of Nobel Peace Prize-winning dissident Liu Xiaobo take part in a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

Supporters of Nobel Peace Prize-winning dissident Liu Xiaobo take part in a candlelight vigil to mark the first anniversary of Liu's death, in Hong Kong, China July 13, 2018. REUTERS/Bobby Yip 

People hold welcome signs as they wait for Liu Xia, widow of Chinese Nobel Peace Prize-winning political dissident Liu Xiaobo, at Tegel airport in Berlin, Germany, July 10, 2018. REUTERS/Hannibal Hanschke 

Pro-democracy activists observe a moment of silence for Liu Xiaobo in celebration with the release of his widow Liu Xia, whose portrait is displayed, in Hong Kong, China July 10, 2018. REUTERS/Bobby Yip 

Pro-democracy activists observe a moment of silence for Liu Xiaobo in celebration with the release of his widow Liu Xia, whose portrait is displayed, in Hong Kong, China July 10, 2018. REUTERS/Bobby Yip 

A woman stands beside a statue of Nobel Peace Prize-winning political dissident, Liu Xiaobo in Hong Kong, China July 10, 2018. REUTERS/Bobby Yip 

A police officer stands guard next to a chair prop, alluding to an empty chair at late Liu Xiaobo's Nobel Peace Prize awarding ceremony in 2010, with an image of his wife Liu Xia, during a protest to urge for the release of Liu Xia, outside the Chinese liaison office in Hong Kong, China December 25, 2017. REUTERS/Tyrone Siu TPX IMAGES OF THE DAY 

A chair prop, alluding to an empty chair at late Liu Xiaobo's Nobel Peace Prize awarding ceremony in 2010, with an image of his wife Liu Xia, is seen during a protest to urge for the release of Liu Xia, outside the Chinese liaison office in Hong Kong, China December 25, 2017. REUTERS/Tyrone Siu 

A chair prop, alluding to an empty chair at late Liu Xiaobo's Nobel Peace Prize awarding ceremony in 2010, with an image of his wife Liu Xia, is seen during a protest to urge for the release of Liu Xia, outside the Chinese liaison office in Hong Kong, China December 25, 2017. REUTERS/Tyrone Siu 

A police officer stands guard next to a chair prop, alluding to an empty chair at late Liu Xiaobo's Nobel Peace Prize awarding ceremony in 2010, with an image of his wife Liu Xia, during a protest to urge for the release of Liu Xia, outside the Chinese liaison office in Hong Kong, China December 25, 2017. REUTERS/Tyrone Siu 

Demonstrators shout during a protest to urge for the release of Liu Xia, wife of late Nobel Peace Prize laureate Liu Xiaobo who was sentenced to imprisonment eight years ago on Christmas, outside the Chinese liaison office in Hong Kong, China December 25, 2017. REUTERS/Tyrone Siu 

Demonstrators hold up images of late Nobel Peace Prize laureate Liu Xiaobo who was sentenced to imprisonment eight years ago on Christmas, during a protest to urge for the release of his wife Liu Xia, outside the Chinese liaison office in Hong Kong, China December 25, 2017. REUTERS/Tyrone Siu 

Demonstrators hold up images of Liu Xia, wife of late Nobel Peace Prize laureate Liu Xiaobo, who was sentenced to imprisonment eight years ago on Christmas, during a protest to urge for the release Liu Xia, outside the Chinese liaison office in Hong Kong, China December 25, 2017. REUTERS/Tyrone Siu 

A protester covers his eyes with red ribbon to call for the release of late Chinese Nobel Peace Prize laureate Liu Xiaobo's wife Liu Xia, in Hong Kong, China August 16, 2017. The banner reads "Missing person. Please help to find Liu Xia." REUTERS/Tyrone Siu 

Protesters carrying candles take part in a march to mourn the death of Nobel laureate Liu Xiaobo in Hong Kong, China, July 15, 2017. REUTERS/Bobby Yip TPX IMAGES OF THE DAY 

Protesters carrying candles take part in a march to mourn the death of Nobel Peace laureate Liu Xiaobo, in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

Protesters carrying candles take part in a march to mourn the death of Nobel Peace laureate Liu Xiaobo, in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

Protesters carrying candles take part in a march to mourn the death of Nobel Peace laureate Liu Xiaobo, in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip TPX IMAGES OF THE DAY 

Protesters chant slogans to mourn the death of Nobel laureate Liu Xiaobo, outside China's Liaison Office in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

A protester holds a defaced Chinese national flag with words "fascist kills Liu Xiaobo", as he mourns the death of Nobel laureate Liu Xiaobo, outside China's Liaison Office in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

A protester carrying a defaced Chinese national flag is blocked by a police officer during a march to mourn the death of Nobel laureate Liu Xiaobo, in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

Protesters carrying candles take part in a march to mourn the death of Nobel laureate Liu Xiaobo, in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

Protesters carrying candles take part in a march to mourn the death of Nobel laureate Liu Xiaobo, in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

Protesters carrying candles take part in a march to mourn the death of Nobel laureate Liu Xiaobo, in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

Protesters carrying candles take part in a march to mourn the death of Nobel laureate Liu Xiaobo, in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

Protesters carrying candles take part in a march to mourn the death of Nobel laureate Liu Xiaobo, in Hong Kong, China July 15, 2017. REUTERS/Bobby Yip 

Liu Xiaoguang, the older brother of deceased Chinese Nobel Peace Prize-winning dissident Liu Xiaobo, addresses reporters in Shenyang, China July 15, 2017. REUTERS/Joseph Campbell 

A supporter holds a sheet of paper reading ''Mourning Liu Xiaobo 1955-2017'' during a ceremony to mourn late Nobel Peace Prize laureate Liu Xiaobo, in Taipei, Taiwan July 14, 2017. REUTERS/Tyrone Siu 

Supporters hold papers reading ''Mourning Liu Xiaobo 1955-2017'' during a ceremony to mourn late Nobel Peace Prize laureate Liu Xiaobo, in Taipei, Taiwan July 14, 2017. REUTERS/Tyrone Siu 

People attend a ceremony to mourn late Nobel Peace Prize laureate Liu Xiaobo, in Taipei, Taiwan July 14, 2017. REUTERS/Tyrone Siu 

Supporters of Chinese Nobel Peace Prize laureate Liu Xiaobo hold flowers during a candlelight vigil in his honour, outside China's consulate in Sydney, Australia July 14, 2017. REUTERS/Jason Reed 

Supporters of Chinese Nobel Peace Prize laureate Liu Xiaobo hold flowers as they memorialise him during a candlelight vigil outside China's consulate in Sydney, Australia July 14, 2017. REUTERS/Jason Reed 

Supporters of Chinese Nobel Peace Prize laureate Liu Xiaobo prepare a makeshift memorial for him, during a candlelight vigil outside China's consulate in Sydney, Australia July 14, 2017. REUTERS/Steven Saphore 

A group bows as they pay their respects in front of a floral memorial for Chinese Nobel Peace Prize laureate Liu Xiaobo outside China's consulate in Sydney, Australia July 14, 2017. REUTERS/Jason Reed 

A group bows as they pay their respects in front of a floral memorial for Chinese Nobel Peace Prize laureate Liu Xiaobo outside China's consulate in Sydney, Australia July 14, 2017. REUTERS/Jason Reed 

Candles are formed in the shape of a heart during a vigil for Chinese Nobel Peace Prize laureate Liu Xiaobo outside China's consulate in Sydney, Australia July 14, 2017. REUTERS/Jason Reed 

A woman places flowers alongside a tribute to Chinese Nobel Peace Prize laureate Liu Xiaobo during a candlelight vigil outside China's consulate in Sydney, Australia July 14, 2017. REUTERS/Steven Saphore 

Candles are formed in the shape of a heart during a vigil for Chinese Nobel Peace Prize laureate Liu Xiaobo outside China's consulate in Sydney, Australia July 14, 2017. REUTERS/Jason Reed