Two charter planes are expected to fly British citizens out of strife-torn Bahrain today as the situation in the country continues to deteriorate.
The Foreign Office has urged people to leave the Gulf state on commercial airlines but is laying on extra flights for those who want to flee and cannot get a ticket elsewhere.
The evacuations from Bahrain to Dubai are due to take place today, with passengers being charged £260 for a seat on one of the charter flights.
The advice to leave comes as running battles were once again fought on Bahraini streets.
Soldiers and riot police used tear gas and armoured vehicles to clear protesters from Pearl Square, which has been the focus of demonstrations in capital Manama.
Prime Minister David Cameron has called on the King of Bahrain to end the violent suppression of street protests.
He spoke by phone to King Hamad bin Isa al-Khalifa and called for restraint from all sides in the stand-off.
Hamad has declared a state of emergency in the island kingdom after a month of demonstrations in which representatives of Bahrain's Shi'ite majority have called for the end of rule by its Sunni monarchy.
Foreign Secretary William Hague has also spoken with Bahraini Foreign Minister Shaikh Khalid Bin Ahmed Bin Mohamed Al Khalifa to express "serious concern" at the situation and urge restraint on all sides and the need for a return to law and order to enable genuine political reform.
Mr Hague said: "The UK remains seriously concerned about clashes with protesters and reports of several casualties.
"I call on all parties to engage in an open and constructive national dialogue, so that it is translated as soon as possible into tangible actions that respond to the legitimate aspirations of the Bahraini people."
Meanwhile, US President Barack Obama urged the kings of Bahrain and Saudi Arabia to show restraint in dealing with protesters.
There have been reports that at least two people were killed during the storming of the square, while local hospital officials said a third died later from gunshot wounds.
Bahrain state TV also reported that two policemen died when they were hit by a vehicle.
Witnesses described helicopters firing on homes in a hunt for Shiites and attacking doctors treating the wounded, while the government called the demonstrators "outlaws" for demanding an end to the monarchy.
The imposition of martial rule followed the arrival of more than 1,000 troops, at the King's invitation, from neighbouring allies including Saudi Arabia.
In a statement the Foreign Office said: "We recommend those British nationals who do not have a pressing reason to remain to leave via Bahrain International Airport on March 17 by commercial means."
It added: "British nationals with commercial flight bookings should continue to use these flights and you should continue to make reservation and ticketing arrangements with your airline as usual.
"The UK Government is chartering planes to supplement commercially available options. These will be available to assist the departure of British nationals from Bahrain to Dubai on March 17."
An FCO spokeswoman added: "Each flight will have 160 seats available. We will assess the need for the number of flights based on demand.
"British Embassy staff will be on hand in Dubai to help people access commercial flights."
It is not known how many Britons are still in the country, but the FCO estimates there are several thousand at any one time.
Those wishing to leave on the Government flights are asked to call +44 20 7008 5900.