Bahraini protesters marking the third anniversary of an Arab Spring-inspired uprising clashed with security forces on Friday in the capital Manama and in outlying villages, witnesses said.
Hundreds of men and women took to the streets in parts of the capital and in Shia villages that have been at the forefront of the campaign among the Gulf state's Shia majority for a consitutional monarchy in the Sunni-ruled Gulf kingdom.
They were met with tear gas and birdshot, the witnesses said, adding that several demonstrators were wounded.
The clashes came ahead of an afternoon march called by an influential cyber-group on the capital's Pearl Square, where demonstrators camped out for a month in early 2011 before being violently dispersed by Saudi-backed troops.
Bahrain announced in June that it had arrested leading members of the February 14 youth coalition, accusing it of links to Shia Iran.
Saudi-led Gulf troops deployed in Bahrain on the eve of the March 2011 crackdown, manning key positions while its own security forces dispersed the protesters.
The Pearl Square roundabout and its central monument, which were a symbol of the uprising, were later razed and the site remains heavily restricted.
"Down with Hamad," the protesters chanted on Friday referring to the king.
"We will never surrender," the crowd shouted as police helicopters hovered overhead, witnesses said.
The Shia opposition called for three days of protests to mark the anniversary as it seeks to give new momentum to its campaign for the ruling Khalifa family to surrender its grip on all key cabinet posts in favour of an elected government.
Amnesty International on Thursday condemned Bahrain's "relentless repression" of dissent and said it feared a violent crackdown on the anniversary demonstrations.
At least 89 people have been killed in the three years since the launch of the uprising, according to the International Federation for Human Rights.