Security forces with tanks have overrun a square in the centre of Bahrain's capital Manama where anti-government protesters have been camped for weeks.
At least three died after police fired on mainly Shia protesters, reports say. Officials said three police died.
The government has imposed a curfew from 1600 (1300 GMT) to 0400 and banned all demonstrations. There are reports of shooting at the main hospital.
The country's Sunni rulers on Tuesday called in Saudi troops to keep order.
At least two people died in clashes on Tuesday and more than 200 were injured.
The country's health minister has resigned in protest against the government's use of force, reports say.
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