Military flights to evacuate British nationals from Sudan as clashes leave over 400 people dead
It comes after British Embassy staff and their families were evacuated over the weekend
British military flights are preparing for a "large-scale" evacuation of UK nationals from Sudan after a three-day ceasefire was agreed.
Foreign Secretary James Cleverly announced that the operation would begin on Tuesday after ministers came under pressure to help at least 2,000 citizens flee the conflict.
RAF flights leaving an airfield outside the capital, Khartoum, will open to British passport holders, with priority being given to the most vulnerable.
The Foreign Office told citizens not to travel there unless they are contacted and warned that the ability to carry out evacuations could change at short notice during the "volatile" truce.
Prime Minister Rishi Sunak said: "The Government has begun a large-scale evacuation of British passport holders from Sudan on RAF flights.
"Priority will be given to the most vulnerable, including families with children and the elderly.
"I pay tribute to the British armed forces, diplomats and Border Force staff carrying out this complex operation."
He said Britain will work to "end the bloodshed" in Sudan, which was triggered by two rival generals engaging in a powerstruggle, and support a democratic government.
Families with children or elderly relatives, or individuals with medical conditions, will be prioritised for the flights.
Only British passport holders and immediate family members with existing UK entry clearance are being told they are eligible.
Nationals have been warned that all travel within Sudan is "conducted at your own risk".
Mr Cleverly said: "The UK Government is co-ordinating an evacuation of British nationals from Sudan.
"We have started contacting nationals directly and providing routes for departure out of the country."
The Foreign Office said other exit routes are being considered, with two British military ships - RFA Cardigan Bay and HMS Lancaster - being lined up for possible evacuations.
A team of British troops is understood to have flown into Port Sudan to check out the options.
Sir Nicholas Kay, a former British ambassador to Sudan, warned that the situation during the ceasefire remains "precarious".
He told BBC Radio 4's Today programme: "The security situation can change very quickly, the command and control over forces isn't complete and there is no trust between the two sides so they might kick off again."
The former diplomat warned that moving around Khartoum could be "very difficult", with the bridges crossing the Blue and White Nile rivers being controlled by the armed groups.
US Secretary of State Antony Blinken announced that a three-day ceasefire had been brokered. It would extend a nominal truce over Ramadan that did little to stop fighting but did facilitate some evacuations.
More than 420 people, including at least 273 civilians, have been killed since fighting began on April 15, and a further 3,700 have been wounded.
The Foreign Office stressed that "senior diplomats" will be supporting the evacuations, after it emerged that British Ambassador to Sudan Giles Lever and his deputy were out of the country when violence broke out in Khartoum.
The latest figure for UK citizens registering with the embassy for evacuation is about 2,000, but the true number of British nationals in Sudan could be higher.
Ministers have been under pressure to get the evacuations under way after a rescue mission of British diplomats was completed over the weekend. European allies have already removed hundreds of citizens.