Bahrain's military says it has taken control of parts of the capital after riot police stormed a main square in Manama early Thursday to drive out thousands of demonstrators.
Western news reports quote the country's health minister as saying three people were killed and 231 wounded in the police operation to clear Pearl Square.
Protesters demanding sweeping political change had set up camp in the square. Security forces firing tear gas, percussion grenades and rubber bullets moved into the square before dawn, attacking the mostly Shi'ite demonstrators - including women and children - who had occupied the area since Tuesday.
Meanwhile, parliament members of the leading Shi'ite al-Wefaq party say the opposition group plans to quit parliament in protest. Earlier, Al-Wefaq leaders said the group's 18 deputies would not return to the 40-member parliament until King Hamad bin Isa al-Khalifa agreed to transform the nation into a constitutional democracy with an elected government.
The Wall Street Journal reported that seven opposition groups, including al-Wefaq, had announced their formation of a committee to help coordinate protest activity and unify the protesters' demands. The Journal said the committee plans large demonstrations on Saturday.
On Wednesday, security forces held back as tens of thousands of Bahrainis gathered, dramatically expanding pro-democracy protests. By nightfall, a massive, jubilant crowd had swelled in Pearl Square following a day of peaceful protests. Earlier, hundreds had joined a procession to mourn one of two demonstrators killed since Monday.
The Khalifa family, which has ruled Bahrain since the 18th century, is Sunni Muslim and has long had tense relations with the country's Shi'ite majority, about 70 percent of the population.
In 2001, voters overwhelmingly approved a national charter to lead the way toward democratic changes. But a year later, the king imposed a constitution by decree that Shi'ite leaders say has diluted the rights in the charter and blocked them from achieving a majority in the parliament.
Bahrain is home to the U.S. Navy's 5th Fleet and also is a regional offshore banking center.
Some information for this report was provided by AP, AFP and Reuters.