Britons are feared to have been stranded in Sudan following reports that the country’s armed forces had prevented a number of people from reaching the last rescue flights out of the war-torn country on Saturday.

On Saturday night, it was announced that 1,888 people on 21 flights have been evacuated from Sudan – the vast majority of them British nationals and their dependants – but the last flight was yet to leave despite being scheduled to depart at 6pm.

Earlier, the Conservative chair of the foreign affairs select committee 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 an airbase north of Khartoum.

Alicia Kearns MP said: “I’ve had some messages saying the Sudanese armed forces have been stopping people from crossing through Khartoum to get to the airstrip. I think we need to look into that and see if that’s got any truth to it. If so, you’ve got British nationals who are stuck and being stopped from getting to the evacuation point.”

Hundreds of people had been told to risk the ongoing fighting and try to make it to the evacuation centre at the Wadi Seidna airbase – about 14 miles north of Khartoum and its twin city, Omdurman – while the Sudanese armed forces continued to attack the positions of the Rapid Support Forces paramilitary group.

Kearns’s bleak update followed fresh airstrikes and artillery fire in the Sudanese capital, and came amid mounting concern over the broader humanitarian disaster unfolding on Sudan’s borders, with thousands waiting for days in the open air to enter Egypt, or walking hundreds of miles to cross into South Sudan.

Among them were Rana Ameen, a 23-year-old engineering student, who said she and five members of her family had paid the equivalent of £475 per person to reach the border crossing with Egypt, almost 600 miles away. To even reach the bus station on the outskirts of Omdurman, the family was forced to negotiate the centre of the capital, where bitter fighting between two generals has caused hundreds thousands of people to flee.

Once at the border, the situation only deteriorated as they were forced to wait in the desert for three days to cross. “It was a deadly trip,” she said. “At the border crossing, there was barely food, water and no bathrooms. Babies were crying as they lay on the ground. Women were very tired. Thousands of men were standing in very long lines to get visas.”

On Friday, the deputy prime minister, Oliver Dowden, said they had imposed the deadline on rescue flights after a lack of demand for seats. However, Kearns urged ministers to check on the location of all 2,000 people who had registered as needing assistance to ensure they had all reached the UK.

She also criticised the communication strategy of the government over the past week as being too intermittent. “The system proves that bureaucratic nonsense and siloed thinking continues to be a problem, even in a crisis,” she added.

On Saturday night shortly after 9pm, the Foreign Office said that the final flight, which had been scheduled to leave at 6pm, was still at the airfield near Khartoum. No reason was given for the delay.

James Cleverly, the foreign secretary, said: “The UK has brought more than 1,888 people to safety from Sudan thanks to the efforts of staff and military working around the clock to deliver this evacuation – the largest of any western country.

“We continue to press all diplomatic levers to secure a long-term ceasefire and end the bloodshed in Sudan. Ultimately a stable transition to civilian rule is the best way to protect the security and prosperity of the Sudanese people.”

Anyone left behind faces an uncertain future and may choose to head north to Egypt, the oppositete way to South Sudan or broadly east towards Port Sudan on the Red Sea.

A sense of Sudan’s rapidly worsening humanitarian crisis began to emerge on Saturday, with images of refugees holding Saudi Arabian flags after successfully crossing the Red Sea to the port of Jeddah contrasting sharply with stories of people waiting days to cross into Egypt.

Thousands more are sheltering in the open border region with Chad, while others have travelled east to Ethiopia.

The International Organization for Migration estimates that at least 75,000 people have been newly displaced by the fighting, although this number may not include thousands more who fled to Sudan to seek shelter from conflict in surrounding nations and have now been forced to flee a second time.

Terrified refugees found little welcome on the border with Egypt, where just a few local police officers had been dispatched to process thousands of exhausted people. “Thousands of people were there at the crossing but very few border employees,” said Ameen, who said there had been only one police officer deployed to check hundreds of passports at a time.

The Egyptian ministry of health said it had deployed teams to two border crossings with Sudan to aid new arrivals in need of care, almost two weeks after fighting began.

Egypt has long sought to militarise its border region with Sudan as a way to crack down on migration, impeding access to civil society or aid groups from the Egyptian side in order to worsen an already harsh environment for arrivals.

Moneer Abdel Mohsen, a Sudanese citizen who fled across the Egyptian border and took a flight back to the United Arab Emirates after a trip to Sudan to see friends, said he had waited a day and a half at the border crossing. “It was chaos at the border,” he said. “People were sitting on the floor. I spent those one and a half days without sleep, food or water.”

He added that prices for bus tickets, which cost him the equivalent of almost £200, are increasing every day. “I felt so sad leaving my friends behind. But only those who have money can leave the country,” he said.

Guardian UK