Police arrived in tanks, troop transport vehicles and buses before moving in and firing tear gas grenades on the mainly Shia Muslim demonstrators.

Hundreds of demonstrators had spent a tense night in the square, many

fearing another police assault on their camp like the one on February 17, in the early days of the uprising, which left four people dead.

Pearl Square has become one of the focal points of the protest movement pressing the country's Sunni rulers for political reforms.

The latest clashes came a day after five of the kingdom's top Shiite clerics warned that a "horrible massacre is expected at (Manama's) Pearl Square against the people of this (Shia) sect, only for peacefully demanding their rights."

In a statement, they appealed for international help in the month long conflict.

Bahrain's King Hamad declared a three month state of emergency on Tuesday, a day after armed forces from Saudi Arabia and the United Arab Emirates entered the country to help deal with the protesters.

Two people died and hundreds were wounded in clashes between anti regime protesters and Bahrain's security forces on Tuesday.

A medic in the village of Sitra, south of the capital, told AFP that armed men had arrived and opened fire with buckshot at residents, wounding 200 people.

More than 200 others were admitted to hospital suffering from tear gas inhalation.

A Shia protester and a member of the security forces were killed in separate incidents in the south of the country.