The Foreign Office confirmed it had ended its rescue efforts on Saturday night, saying: "The last evacuation flight departed Wadi Saeedna airfield at 2200 Sudan time (9pm BST) on 29 April."

The Foreign Office said the evacuation of British nationals and some NHS doctors without UK passports had been the largest of any Western nation from the country.

Those who could not fly are seeking refuge by crossing Sudan's land borders.

Despite a ceasefire lasting up until midnight on Sunday, gunfire and heavy artillery in parts of the capital Khartoum have been reported by residents.

The civilian death toll jumped to 411 and the number of injured to 2,023, according to the Sudan Doctors' Syndicate, which measures casualties.

More than 50,000 Sudanese refugees - mostly women and children - have crossed over into Chad, Egypt, South Sudan and the Central African Republic since the crisis began, the United Nations said.

It said the diaspora risks raising regional instability, with South Sudan and the Central African Republic scarred by years of ethnic fighting and turmoil and Chad's own democratic transition derailed by a 2021 coup.

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Meanwhile, former Sudanese prime minister Abdalla Hamdok said the conflict must stop and warned of the consequences not just in Sudan but for the region.

"This is a huge country, very diverse... I think it will be a nightmare for the world," he told a news conference in Nairobi. "This is not a war between an army and small rebellion. It is almost like two armies - well-trained and well-armed."

Khartoum, a city of some five million people, has become a front line in the fighting between General Abdel Fattah Burhan, the commander of Sudan's military, and General Mohammed Hamdan Dagalo, who leads the powerful paramilitary group known as the Rapid Support Forces.

Those who escape the city face further obstacles, with a long and risky overland journey to Port Sudan, where ships have been evacuating people via the Red Sea.

The UK government has said it remains committed to supporting British nationals who remain in Sudan and its focus would now turn to providing consular support to British nationals in Port Sudan and neighbouring countries in the region.

Airlifts have also faced challenges, with a Turkish evacuation plane hit by gunfire outside of Khartoum on Friday.

Civilians running out of food and supplies

Fighting continued around the presidential palace, the headquarters of the state broadcaster and a military base on Saturday, residents said, despite a ceasefire extended by another 72 hours on Friday under heavy international pressure.

Columns of thick black smoke billowed over the capital city's skyline.

Those sheltering at home amid the conflict, which is now in its third week, have warned they are running out of food and basic supplies.

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While the military has appeared to have the upper hand in the battle to control Africa's third-largest nation, there is little hope the conflict will end anytime soon.