Protesters have been detained by police in the Azerbaijani capital Baku.
Protesters took to Baku's streets last Sunday
Several hundred opposition supporters were trying for the second weekend in a row to hold a rally, in defiance of a government ban.
Police detained at least 50 people, herding them into minibuses. Opposition activists accused them of brutality.
The opposition is protesting against what they say is the government's failure to ensure a fair campaign for November's parliamentary election.
A spokesman for the People's Front of Azerbaijan, part of the opposition Azadlig alliance, said protesters had been "brutally stopped" by police.
Isak Avazogli said one activist had been badly beaten and had been taken to the party headquarters to wait for an ambulance.
"The opposition says more then 200 of their activists have been arrested. Among them are many candidates for the parliament," said the BBC's Natalia Anteleva from Baku.
She said a group of women calling for free elections were chased down a street by police and beaten with batons.
"They're mocking people and showing great cruelty to women," said Saida Godzhamanly, head of the Bureau of Human Rights and Observance of Legality.
"This is as bad as the previous protest, when on one side there was force, truncheons and shields, and on the other dreams of democracy."
About 10,000 opposition activists had gathered in rallies in various streets of the capital, but were unable to make their way to the city's main square.
Fears of unrest
Saturday's protest followed the beating and arrest of dozens of people last Sunday amid clashes between opposition supporters and riot police.
There are fears of worsening political unrest in the oil-rich Caspian nation, a former Soviet state.
Parliamentary elections are only weeks away. The opposition alliance has said the government had turned its back on promised talks, making public demonstrations their only option.
President Ilham Aliev - who succeeded his father Geidar Aliev in a 2003 election the opposition have accused of being rigged - had promised the November elections will be fair.
The opposition have said they will push for revolution if it is not.