Police in Azerbaijan's capital, Baku, have used truncheons, tear gas and water cannon to disperse a mass protest over the 6 November election results.
Some of the injured appeared seriously hurt, witnesses said
Injuries were reported as they cleared a square on the city's edge where some 10,000 protesters were attempting to begin an open-ended sit-down protest.
It was the first use of police force against a rally since the election.
The opposition say the results giving President Ilham Aliyev's party overwhelming victory were falsified.
Alleged irregularities and fraud have also alarmed the international community.
Saturday's demonstrators had defied a limit of two hours on their rally.
The Azeri opposition was previously careful to abide by government restrictions on protests to avoid confrontation with the police, says the BBC's Natalia Antelava in Baku.
Hundreds of policemen in full riot gear had lined the edges of Victory Square for the latest of a series of tightly controlled demonstrations.
Protesters wanted to stage a permanent sit-in this time
Ali Kerimli, a leader of the Azadlyg opposition bloc, called on the protesters to remain in the square and begin an open-ended protest - similar to that which began Ukraine's "Orange Revolution" in Kiev last year.
He called on them not to resist the police but to sit down if they tried to move them on.
Police then moved in, beating protesters with truncheons and firing teargas, witnesses say.
Water cannons were also used against the crowd - reportedly for the first time since the election.
Many of the protesters ran away, some of them throwing stones at the police. A number were reportedly arrested and loaded into police buses.
Mr Kerimli later told Reuters news agency that a "lot" of demonstrators had been hurt.
"We were having a peaceful protest which ended when police started to beat up unarmed people," he said.
Upping the ante
Many activists say the time has come to put more pressure on the government and stay in the square, our correspondent says.
Their inspiration, they say, comes from Ukraine and Georgia, where fraudulent elections sparked mass protests and forced change.
Leaders of the opposition United Freedom Bloc have insisted on a re-run of the vote.
But President Aliyev, son of the late Heydar Aliyev, says that in his oil-rich state the chances of an Orange Revolution are zero.