(Reuters) - Bahraini police detained two Western activists who had joined a women's protest on Friday, after clashing overnight with protesters in Shi'ite districts of the Gulf Arab state.
The two women activists - one American, one British, according to protesters - were detained by riot police who broke up the protest with teargas and stun grenades, after an announcement on a police loudspeaker that the demonstration was illegal.
Riot police have maintained a heavier presence than usual in areas populated by majority Shi'ites this week to prevent mass protests on the anniversary of the February 14 pro-democracy uprising last year which was put down by force.
"These women are protesting peacefully," shouted a woman identified by protesters as U.S. activist Medea Benjamin, wearing a T-shirt that read "Unarmed civilian," as she was dragged away by women police.
A Bahraini woman choking from teargas was also dragged away.
Protesters identified the second detained foreign activist as Briton Elaine Martha. Bahrain has already arrested and deported around eight foreign activists in the past few days.
Later on Friday, large police forces used water cannons to try to disperse several hundred demonstrators in the northern district of Jidhafs. Protesters ran into side streets, only to regroup and reappear in a nearby area.
In the district of Sar, police fired volleys of stun grenades and teargas to break up groups of teenagers who threw stones and petrol bombs late on Thursday.
Police said an improvised explosive device (IED) containing nails had been thrown at them. In the nearby village of Bani Jamra, site of another protest, police said they had defused another IED.
Some residents shouted anti-government slogans and the Muslim rallying cry "Allahu akbar" - God is greatest - from inside their homes or on rooftops.
An Interior Ministry statement said two policemen were seriously injured in a petrol bomb attack late on Wednesday in the town of Sitra. Residents say at least 15 people were later arrested that night.
A medic said at least 120 people were wounded earlier this week. Police have not said how many people they arrested.
Bahrain has been in turmoil since last year's uprising, mainly by majority Shi'ites complaining of political and economic marginalization by the Sunni royal Al Khalifa family.
The authorities were determined to prevent protesters returning to a symbolically important central roundabout in the capital this week to mark the first anniversary of the uprising.
Riot police and national guard forces maintained tight security near the roundabout, which is partly surrounded by barbed wire, and for the first time since a period of martial law last year deployed armored vehicles in Shi'ite villages.
The opposition want a shift to fully fledged parliamentary democracy where the elected house forms cabinets, but the government has so far offered only reforms that allow parliament greater powers of scrutiny over ministers and budgets.