Bahraini police used tear gas and stun grenades to disperse dozens of anti-regime Shiite demonstrators who staged a protest in central Manama on Monday to mark the opposition's "Martyrs' Day", witnesses said.
The protesters had gathered in the financial district in response to calls by the online activist group February 14th Youth, they said, adding that plainclothes police made several arrests.
Demonstrators chanted anti-monarchy slogans, including "Down (King) Hamad," and the "people want the fall of the regime."
The demonstration was held despite tight security, as authorities have not authorised protests in Manama since a month-long protest camp was demolished in mid-March 2011.
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Shiite protesters stage protests mostly in their villages outside Manama.
Also on Monday, protesters clashed with police in a number of villages and blocked main roads with burning tyres, witnesses said.
Martyrs' Day commemorates the deaths of regime opponents in clashes with security forces in the 1990s.
Bahrain was shaken by a protest movement in February 2011 led by the Shiite majority demanding a constitutional monarchy in the Sunni-ruled kingdom.
At least 80 people have died since the start of the unrest, according to the International Federation of Human Rights.
Last week, Bahrain's crown prince made a renewed appeal for dialogue to end a political impasse, in a call welcomed by the opposition as protests turn increasingly violent.