On Thursday, security forces raided the protesters camped out in Pearl Square in central Manama and fired tear gas and rubber bullets at the people to disperse them, Reuters reported.
At least 2,000 protesters were occupying the Pearl Square on Wednesday, calling for a new constitution and an elected prime minister.
More than a dozen army tanks and several military ambulances and trucks are seen in a main highway in the central Manama.
Security forces have also put up barbed wire around Pearl Square.
On Wednesday, Bahraini authorities said that they would seek to restore calm in the streets on Thursday, after days of protests inspired by the revolutions in Tunisia and Egypt and intensified by the deaths of two protesters in 24 hours.
The magnitude of the pro-democracy protests in Bahrain is unprecedented in the history of the kingdom and the authorities' efforts to quell them have so far been ineffective.
Bahrain is ruled by a royal family from the country's Sunni minority, who are blamed for discrimination against the country's Shia population ~ comprising 70 percent of the population.
Protesters have called on the Bahraini to fire his uncle, Khalifa bin Salman al-Khalifa, who has been the country's prime minister since 1971.