Observers for rights groups expelled amid security clampdown to prevent mass pro-democracy protests in capital.
Bahrain announced the deportation of four foreign activists for «taking part in illegal demonstrations» in the country, adding to a number of deportations of activists over the past week.
The four activists were deported for «lying on immigration forms» as their «visas were issued for the purposes of tourism but all were participating in illegal demonstrations», the official BNA news agency reported late on Friday.
The news agency did not specify the nationalities of those deported. The main Shia opposition group, Al-Wefaq, said they included one American and one Briton.
Police detained, and later deported, Medea Benjamin, an American with the observer group Witness Bahrain. Elaine Murthagh, an Irish-British activist, was also deported.
Benjamin and Murthagh, joined a protest with a group of about 150 women that clashed with riot police, which including a group of female officers, for several minutes on Friday.
Police told the group to disperse, then threw a round of stun grenades and tear gas at the women. One woman was dragged away by female riot police after she was pepper-sprayed.
«These women are protesting peacefully,» Benjamin shouted as she was being dragged away.
Reuters news agency reports that at least 10 foreign activists have been deported this week. An opposition member said as many as 15 foreign activists had been deported in the last five days.
The authorities have recently increased restrictions for foreign activists and international media, denying press visas to several news organisations.
Bahraini police also deployed a water cannon on Friday and armoured vehicles against an anti-government demonstration of around 500 people from the majority Shia population following a funeral.
Bahrain has imposed a security clampdown this week in a bid to avert mass protests on the anniversary of the February 14 pro-democracy uprising last year in which four people were killed.
The clampdown also aimed to prevent Shias from reaching the Pearl Roundabout, a junction in capital Manama that has became the focal point of protests.
Nabeel Rajab, an activist with the Bahrain Centre for Human Rights told Al Jazeera: «The Bahrain government launched armoured vehicles… almost in each and every village in Bahrain.»
Rajab said there have been continuous protests in Bahrain since February 14.
«Tens of thousands of people came out in the street, many of them were heading to the Pearl Roundabout and they were attacked,» Rajab said.