Foreign Secretary James Cleverly has told broadcasters that the situation is Sudan is very dangerous, but the UK is working “as quickly as possible” to evacuate trapped Britons.
He said the UK was unable to help Britons get to the airfield north of the capital, Khartoum, and warned that it was unclear how long the ceasefire would hold.
The ceasefire provides a 72-hour window.
The US-Saudi mediated truce between the Sudanese military and Rapid Support Forces (RSF) paramilitary group began on Monday night and followed two days of intense negotiations. Two previous ceasefires have not held.
Mr Cleverly said: “It is important to remember that ceasefires have been announced and have fallen apart in the past, so the situation remains dangerous, volatile, and unpredictable.
“Of course, it is impossible for us to predict how long this opportunity will last, and we’re calling people forward in priority order based on their vulnerability.”
Asked how Briton could safely reach the airfield where RAF jets are landing to evacuate Brits, Mr Cleverly said: “The truth is we cannot predict how the situation on the ground will develop.
“The conflict has been unpredictable, it’s been volatile.
“We have said that we are unable to provide escorts from where British national are to the airfield. They will have to make their own way there.”
He said that the armed forces would keep the airlifts going “as long as we can”.
“We are providing what assistance that we can and we are operating as quickly as we can,” he insisted.
He also said the situation was “fundamentally different” to the chaos witnessed during the evacuation from Afghanistan.
Defending the government against allegations that the UK acted slowly to evacuate Britons, Mr Cleverly said: “The circumstances for each individual nation are different. There are considerably more British nationals in Sudan than other countries have got.”
RAF plane takes off north of Khartoum
A Royal Air Force plane has departed an airfield north of Sudan’s capital Khartoum and is heading to the RAF Akrotiri military base in Cyprus.
The flight landed in Sudan just before 09:00 BST and then departed just after 09:30.
It is a military transport aircraft which can land on rough terrain and can hold around 100 people.
Chair of the foreign affairs committee Alicia Kearns says they believe there are 3,000 to 4,000 British nationals there.
Speaking to BBC Breakfast, the Conservative MP says that they don’t know if everyone wants to leave Sudan but they are aiming to get everyone who wants to leave the country out.
“Because” she says, “We can’t be confident the ceasefire will hold”
“The foreign office is contacting every single British citizen who is registered. Stay tight, because outside is still not safe. Gather your belongings, get ready for the journey. Make sure you have the most signal possible.
“You don’t need to rush to the airport. The Foreign Office needs to make sure you make a safe trip to the airport.”