MOSCOW (REUTERS) - A Russian judge on Friday convicted eight defendants of rioting and assaulting police at a protest against Vladimir Putin, in what one of his leading critics called a "show trial" designed to make clear the president would tolerate no dissent.

In a show of force outside the courthouse, police pushed into a crowd of hundreds that had gathered to support the defendants, grabbing people one by one and hauling them away.

Moscow police said they detained about 200 people for attempting to violate public order.

The convictions, which activists had anticipated, coincided with political turmoil in neighbouring Ukraine, where dozens have died in violence the Kremlin blames on militant government opponents it accuses the West of encouraging.

The defendants - seven men and a woman mostly in their 20s - were found guilty of rioting and violence against police at an opposition protest on May 6, 2012, the eve of Putin's inauguration for a third term as president.

Putin's opponents blame the police for clashes at that rally on Moscow's Bolotnaya Square - one of a series of protests that were the most concerted during his long rule but failed to prevent his return to the Kremlin after four years as prime minister.

They say it was part of a fresh clampdown on dissent by Putin, first elected in 2000, that has included restrictive laws, accusations of Western meddling and the jailing of critics such as members of Pussy Riot.

Putin has denied he uses the courts as a political tool, and has said violence against police must not go unpunished.

Two women from the protest band were in the crowd outside the court, as was Alexei Navalny, who emerged from the wave of protests as the top opposition leader and is serving a five-year suspended sentence after a theft trial last year he said was Kremlin revenge.

All eight defendants pleaded not guilty. By law, each could be sentenced to up to eight years in prison, but prosecutors asked the judge to hand down sentences of five to six years.

After starting the hearing more than three hours behind schedule, judge Natalya Nikishina abruptly ended it late in the afternoon and said she would pronounce the sentences on Monday.

That means they will be passed after Sunday's close of the Sochi Winter Olympics - a prestige project for Putin, who has faced criticism from the West for his treatment of dissent in his third presidential term.

Shouts from the street of "Shame!" and "Free them!" drifted into the cramped fourth-floor courtroom where the male defendants, who have been in custody since 2012, stood handcuffed in a metal cage as Nikishina read out the verdict.

Some ignored the judge, exchanging glances with their wives and girlfriends instead.

Repeating parts of the indictment word-for-word, Nikishina detailed how each defendant had attacked police.

She said Alexandra Naumova, 20, who is under house arrest pending sentencing and stood holding hands with her husband in the courtroom, had thrown stones, bottles and chunks of asphalt at police at the protest.

The judge said she threw eight objects at police. Her lawyer, Dmitry Dubrovin, said after the hearing there was only one instance in which she may have done so and that had not been proven in court.

Nobody was killed at the 2012 protest and the defendants are not charged with endangering the lives or health of police.

One was accused of hitting an officer with an "unidentified hard, yellow object" that his lawyers say was a lemon.