The UK government has announced plans to carry out an additional evacuation flight from Sudan on Monday, after previously suggesting that efforts to bring British nationals out of the war-torn country had concluded. In a statement on Sunday, the Foreign, Commonwealth and Development Office (FCDO) urged any UK nationals still hoping to leave Sudan to make their way to the airport in Port Sudan, on the Red Sea coast, by noon local time (11am BST) on 1 May. The flight that left Wadi Seidna airport, just north of the capital, Khartoum, late on Saturday night had been expected to mark the end of the evacuation. The FCDO minister Andrew Mitchell told the BBC the operation had been “extremely successful”, but added: “We can’t stay there for ever in such dangerous circumstances.” The number of people evacuated by the government has reached 2,122, on 23 flights, the FCDO said on Sunday, calling it “the longest and largest evacuation effort of any western country from Sudan”. Ministers were initially criticised for a slow response to the crisis, with some UK citizens trapped in Sudan complaining of poor communication and lack of support. The foreign secretary, James Cleverly, confirmed there would be no further evacuation flights from Wadi Seidna. “Evacuation flights have ended from Wadi Seidna but our rescue efforts continue from Port Sudan. We continue to do everything in our power to secure a long-term ceasefire, a stable transition to civilian rule and an end [to] the violence in Sudan,” he said. The Conservative chair of the foreign affairs select committee, Alicia Kearns, told the Observer she had received information that elements of the Sudanese armed forces had blocked British nationals as they attempted to navigate the treacherous route to the airbase north of Khartoum. The extension of the UK evacuation follows a last-minute U-turn by the government to allow NHS workers to join British nationals trapped in Sudan on to flights on Saturday. It came after a doctors’ union called for NHS medics without UK passports to be included in the airlifts. The FCDO confirmed that evacuation criteria had been expanded on Saturday to include “eligible non-British nationals in Sudan who are working as clinicians within the NHS, and their dependants who have leave to enter the UK”. Thousands more British citizens may yet remain in Sudan against a backdrop of continued fighting in Khartoum. Sudan’s army and its rival paramilitary said on Sunday they would extend a humanitarian ceasefire for a further 72 hours. The move follows international pressure to allow the safe passage of civilians and aid, although it has not stopped clashes continuing to break out. Sudan’s former prime minister Abdalla Hamdok has warned that the conflict in the turbulent African country could deteriorate into one of the world’s worst civil wars if it is not stopped soon. More than 500 people have been killed since battles erupted on 15 April between the forces of the army’s commander-in-chief and Sudan’s de facto ruler, Abdel Fattah al-Burhan, and the country’s deputy leader, Mohamed Hamdan Dagalo, commonly known as Hemedti, who commands the paramilitary Rapid Support Forces. “God forbid if Sudan is to reach a point of civil war proper … Syria, Yemen, Libya will be a small play,” Hamdok said in a conversation with Sudan-born telecoms tycoon Mo Ibrahim at an event in Nairobi. “I think it would be a nightmare for the world,” he said, adding that it would have many ramifications.