A riot police officer clashes with demonstrators during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. Police fired tear gas and rubber bullets at demonstrators hurling rocks in a rural Hong Kong town as several thousand activists gathered to protest an attack by suspected triad gang members at a train station the previous weekend. REUTERS/Tyrone Siu

Police officers fire tear gas at demonstrators during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. Activists held the march in Yuen Long, scene of the attack by club-wielding men, despite a police ban on safety grounds. REUTERS/Tyrone Siu

A fire extinguisher is seen thrown at riot police during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. Building barricades out of street furniture and umbrellas, protesters threw rocks and bottles. Many armed themselves with hiking sticks and improvised shields from wood, surfboards, cardboard and other materials. REUTERS/Tyrone Siu

Demonstrators clash with police during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

A police officer fires tear gas at the demonstrators during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Demonstrators clash with police during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Police officers use pepper spray during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Demonstrators use shields and umbrellas to protect themselves during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

Police officers use pepper spray during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

Demonstrators use shields to protect themselves during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Demonstrators react as riot police fire tear gas during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Police officers fire tear gas at demonstrators during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Demonstrators throw umbrellas at riot police during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Riot police clash with protesters inside a train station during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

A protester throws a fire extinguisher as he tries to stop riot police to get inside a train station during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

A reporter reacts after being hit by tear gas during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

A police officer reacts during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

A demonstrator shouts at riot police amidst smoke during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

A demonstrator is seen injured during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Demonstrators clash with police during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

A demonstrator is seen injured by a rubber bullet during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Demonstrators clash with police during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

Demonstrators are seen amidst smoke from tear gas during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

Demonstrators use umbrellas during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Demonstrators are seen at a train station during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

Demonstrators are seen amidst smoke from tear gas during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

A demonstrator rests during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

Demonstrators march to protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

A lawmaker Roy Kwong reacts after the tear gas and pepper spray was used by police during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

A demonstrator reacts to tear gas during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Police officers use pepper spray during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

Demonstrators clash with police during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

Police officers fire tear gas and use pepper spray at the demonstrators during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

Police officers fire tear gas during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Tyrone Siu

A damaged car is seen during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su

Police officers are seen during a protest against the Yuen Long attacks in Yuen Long, New Territories, Hong Kong, China July 27. REUTERS/Edgar Su