MANAMA, Sept 7 Police fired tear gas and stun grenades at dozens of anti-government protesters who defied a ban on unauthorised demonstrations and marched in the centre of Bahraini capital Manama on Friday.
Bahrain, where the U.S. Fifth Fleet is based, has been in political turmoil since a protest movement dominated by majority Shi'ite Muslims erupted in February 2011 during a wave of revolts against authoritarian governments across the Arab world.
The Sunni Muslim ruling Al Khalifa family put down the uprising with martial law, troops from Saudi Arabia and police from the United Arab Emirates, but unrest has resumed, with almost daily clashes between Shi'ites and police.
Armoured vehicles and riot police closed off some of the main roads leading into the city but protesters still made it to Friday's march, which had been called by Bahrain's main opposition bloc Al Wefaq and tweeted as "freedom for prisoners of conscience".
Last week, a march attended by tens of thousands of demonstrators that had also been organised by Al Wefaq together with other opposition groups and which the authorities had approved passed without incident.
On Tuesday, a Bahraini civilian court upheld jail sentences of between five and 25 years against leaders of last year's pro-democracy uprising, a decision that could fuel more unrest in the small Gulf Arab state. Al Wefaq condemned the ruling.
Opposition parties led by Al Wefaq are demanding full powers for the elected parliament to legislate and form governments. Many Shi'ites complain of being politically and economically marginalised, which the government denies.