The unofficial death toll in Bahrain's latest anti- government protests rose to five on Thursday as the country's police and military tightened their grip on the capital Manama, dpa reported
Unconfirmed reports said another protester had died as a result of riot police breaking up a protest camp in Manama's central Pearl Square. So far, government officials have confirmed three deaths. Hundreds more are believed to have been injured.
The Interior Ministry has vowed to take the necessary steps to ensure security and break up the demonstrations, which have been declared illegal.
A column of at least 25 tanks was seen moving along a main highway of the capital, where thousands of protesters have been campaigning for change. Despite the warnings, the protesters were expected to resume their campaign later in the day.
Meanwhile, 18 lawmakers from the Shia opposition confirmed they were resigning.
The news came after a Foreign Ministry official and a popular human rights activist resigned in protest at the government's crackdown on demonstrators.
Nazar Al-Bahrnah, minister of state for foreign affairs, and Abdullah Al Durazi, who had been tasked with overseeing a national reconciliation committee, both stepped down in protest at the government's actions.
The demonstrations have sparked alarm in the United States, since Bahrain is a key US ally and hosts the US Navy's Fifth Fleet.
There is also concern surrounding the Bahrain Grand Prix, which kick-starts the Formula One season on March 13.
An estimated 5,000 people had gathered in Pearl Square early Thursday. The police used tear gas and opened fire without warning to disperse the crowd, witnesses told the German Press Agency dpa.
Inspired by recent events in Tunisia and Egypt, Bahrain's protesters are no longer demanding democratic reforms, insisting they will accept nothing less than a regime change.
"People want to bring down the regime," was a popular slogan chanted by demonstrators in Manama.
Doctors and nurses have reacted furiously after government officials ordered hospitals not to dispatch ambulances to treat the injured.
Bahrain's demonstrations were triggered by the ouster of former president Hosny Mubarak in Egypt. Bahrain is a constitutional monarchy. Its prime minister, Khalifa ibn Salman Al Khalifa, has been in power since 1971 - the longest-serving unelected prime minister in the world.
Meanwhile, a practice session for this weekend's GP2 Asia Series race was called off Thursday "due to the current local events," organizers said in a statement.
"The medical staff normally stationed at the circuit has been temporary called to the city's hospitals in case of an emergency.
"For obvious safety reasons, the GP2 Series organisers have decided to postpone todays track activity until tomorrow," the statement said