Thousands of people had been occupying the site since Tuesday, after two other demonstrators were killed in earlier anti-government protests.
The US said yesterday that it was watching events in Bahrain "very closely" as thousands of Bahrainis protested in the street and called for a "real constitutional monarchy". However, Bahrain’s authorities said they had no choice but to disperse the protesters.
"The security forces evacuated Pearl Square ... after having exhausted all chance of dialogue," interior ministry spokesman General Tarek al-Hassan said, in a statement from the official news agency BNA.
"Some left the place of their own accord, while others refused to submit to the law, which required an intervention to disperse them.”.
The leader of the main Shia-Muslim opposition group condemned the crackdown as a "savage and unjustified attack against a peaceful assembly".
"This attack was a mistaken decision which will have catastrophic repercussions on the stability of Bahrain,” Sheikh Ali Salman, head of the Islamic National Accord Association (INAA), told French press agency AFP.
Relatives named two of the dead men as Mahmoud Makki Ali, 22, and Ali Mansour
Ahmad Khoder, 52. Another man is reported to have been shot dead.
"Hussein Zaid was shot by a hollow-point bullet in his chest and died at Salmaniya hospital in Manama," said Ali al-Aswad, an MP from the Al-Wefaq Shia opposition bloc.