Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, Russia July 27, 2019. Russian police rounded up more than 1,000 people in Moscow on Saturday in one of the biggest crackdowns of recent times against an increasingly defiant opposition decrying President Vladimir Putin’s tight grip on power. REUTERS/Shamil Zhumatov 

A law enforcement officer stands guard during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. The detentions came around a protest to demand that opposition members be allowed to run in a local election. Authorities had declared it illegal and sought to block participation, but several thousand people turned up anyway in one of the longest and most determined protests of recent years. REUTERS/Maxim Shemetov 

People take part at a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. The placard reads: "I have a right to my candidate". Chants of "Russia without Putin" and "Putin resign" echoed through central Moscow as guardsmen clad in riot gear beat back protesters with batons and roughly detained people. REUTERS/Maxim Shemetov 

Protesters take part at a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers clash with protesters during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Tatyana Makeyeva 

A man reacts inside a police bus after he was detained during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers block a street during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Protesters attempt to remove fences during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Tatyana Makeyeva 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Tatyana Makeyeva 

Law enforcement officers block a street during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Tatyana Makeyeva 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Tatyana Makeyeva 

Law enforcement officers detain a protester during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Shamil Zhumatov 

Law enforcement officers clash with protesters during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Shamil Zhumatov 

Law enforcement officers detain a political activist Maria Alyokhina during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Tatyana Makeyeva 

People take part at a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Shamil Zhumatov 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Tatyana Makeyeva 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Shamil Zhumatov 

Protesters carry a bench during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

A woman on a wheelchair is seen in front of law enforcement officers blocking a street during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers detain protesters during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers detain protesters during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

Law enforcement officers detain participants of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. The placard reads: "Better rally!" REUTERS/Shamil Zhumatov 

Law enforcement officers detain a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

A law enforcement officer detains a participant of a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Maxim Shemetov 

A woman talks with a law enforcement officer during a rally calling for opposition candidates to be registered for elections to Moscow City Duma, the capital's regional parliament, in Moscow, July 27. REUTERS/Tatyana Makeyeva