Russian celebrities, most of whom usually steer clear of politics and have millions of followers on social media, said the case tarnished the reputation of authorities.
Russian celebrities have launched a major solidarity campaign in support of a young actor who they say was wrongfully jailed for a crime amid a crackdown on the opposition.
On Monday, a Moscow court sentenced 23-year-old actor Pavel Ustinov to three and a half years in prison for violence against police at an opposition protest even though he claimed he was simply a bystander.
His conviction brought to six the number of people sentenced to jail time ranging from two to four years for taking part in a recent wave of anti-government demonstrations.
But Ustinov's sentencing sparked particular outrage because the court refused to consider video footage that showed police in an apparently unprovoked attack on the actor.
The celebrities, most of whom usually steer clear of politics and have millions of followers on social media, said the case tarnished the reputation of authorities.
"I think that this is a completely trumped-up case," film actor Alexander Pal said in a video posted on Instagram.
Pal, who helped kickstart the campaign, said the video proved his innocence.
Footage from the scene showed police in full riot gear lunging at Ustinov – who was standing with a phone in his hand near a metro station – and beating him with batons.
Danila Kozlovsky, a Russian star who appeared in the British TV series McMafia, said the "monstrous injustice and cynicism with which it's being done can happen to everyone."
The celebrities compared Ustinov's case with that of journalist Ivan Golunov detained in June on trumped-up drug charges.
He was freed after an unprecedented campaign of solidarity, which saw three major newspapers publish the same front page with the headline "I am/we are Ivan Golunov".
In a similar vein, dozens of celebrities and lesser-known figures posted "I am/we are Pavel Ustinov" on their Instagram accounts.
Supporters included actor Alexander Petrov, who has 2.1 million followers on Instagram, singer Andrei Makarevich and star blogger Yury Dud.
In a video, Maxim Galkin, a Kremlin-friendly impersonator and comedian, called the case against Ustinov a "colossal overkill" that deals a major blow to the reputation of courts, law enforcement agencies and authorities.
In comments posted alongside the video, Galkin, who is the husband of Soviet-era pop diva Alla Pugachyova and has 6.4 million followers on Instagram, added he was not interested in politics but supported freedom.
His post racked up more than 780,000 views as of Tuesday afternoon.
Sentences 'must be reviewed'
Actors at several theatres also backed Ustinov during curtain calls on Monday night.
"We believe this to be an awful injustice," director Alexander Molochnikov said on stage after a performance at the Chekhov Moscow Art Theatre.
And in a rare move, some 40 Orthodox priests voiced support for the protests in an open letter published in the online journal Pravmir, which covers religious issues.
"It is our duty to express the opinion that the prison sentences given to several people in this affair must be reviewed," said the letter which called the conviction of Ustinov an act of "cruelty without precedent."
Kremlin spokesman Dmitry Peskov said Vladimir Putin was aware of the case but could not interfere, and that Ustinov had a right to appeal.
Investigators said Ustinov violated public order during an unauthorised rally on August 3 and put up resistance during his arrest. As a result, a policeman sprained his shoulder.
Ustinov has insisted he is innocent.
Tens of thousands of people rallied in Moscow this summer after authorities refused to allow opposition candidates to stand for the city parliament in September 8 elections.
While some of those jailed were activists, others like Ustinov or entrepreneur Danila Beglets were merely bystanders who got caught up in the authorities' crackdown, observers say.
Many welcomed the campaign, but some said solidarity between actors was not enough.
"Until actors begin to take to the streets in support for teachers and teachers in support of economists, nothing will change," opposition politician Dmitry Gudkov said.
Earlier this month, a Russian judge halted the embezzlement trial of acclaimed theatre director Kirill Serebrennikov, whose detention had attracted international attention and calls for his release everywhere from Hollywood to Cannes.