The Foreign Office has warned British citizens still stuck in Afghanistan to “consider carefully the risks” involved in trying to flee. The foreign secretary, Dominic Raab, acknowledged that hundreds of British nationals had been left behind after all evacuation flights out of Kabul ended. Several of those who remain in the Afghan capital said they were struggling to get through to a Foreign Office emergency helpline, had received no personalised response to emails asking for help and were awaiting clear information about what to do next. One British citizen, a 42-year-old minicab driver from south London who spent five days last week queueing with his wife and baby outside Kabul airport, said he had received an automated Foreign Office email telling him what he already knew. “British nationals who remain in Afghanistan need to consider carefully the risks should they attempt to leave by any route,” the email said, adding that the risk of terrorist attacks around the airport “remains very high”. It said the Foreign Office “cannot offer advice on the safety or travelling to any alternative departure point”. The message concluded: “Any travel options you pursue are taken at your own risk. All travel throughout Afghanistan is extremely dangerous, and border crossings may not be open.” The minicab driver said: “They are just automatic responses, sent to everyone by a machine. It’s just a robot answering, and this isn’t at all helpful.” In the past few days he had decided to leave his relatives’ home in Kabul because he felt nervous about remaining where neighbours knew a British citizen has been living. Raab, when asked on Tuesday about British nationals who remained in Afghanistan, said it was hard to give a firm estimate of how many there were, estimating it was likely to be “in the low hundreds”. He said more than 5,000 UK passport holders had been helped to return home since April. The Foreign Office had been advising British nationals to leave Afghanistan and return to the UK since May, he told the BBC. Many of the British citizens now struggling to get back to the UK said they had travelled to Afghanistan this summer, as the severity of the situation became clear, in order to try to bring their children to safety. Some are former refugees who fled to the UK after coalition forces invaded Afghanistan 20 years ago in the wake of 9/11. Although they have acquired British citizenship, the process of applying for passports for wives and children in Afghanistan is protracted. Many said they were concerned about how dependants who do not have British passports would be able to get out of the country now that all UK consular staff have left. Several said they had been told by British officials during the early stage of the evacuation process in mid-August that their spouse and any dependent children under the age of 18 would be eligible for spaces on flights to the UK. They received emailed invitations to make their way to the British-run Baron hotel processing centre near the airport with their families but found themselves blocked by crowds and unable to get to the gates, and had to abandon the attempt to leave. Downing Street has said it is increasing staff numbers in countries neighbouring Afghanistan to help evacuate those who can travel overland to escape. Boris Johnson’s official spokesperson said: “We are beefing up the number of [surge] staff in neighbouring countries – Foreign Office and other staff – to support that.” But some British nationals said they were unclear on how to exit Afghanistan into neighbouring countries given that their children would be travelling without passports. The Foreign Office has asked UK nationals in Afghanistan to confirm their presence using a new online registration form. One Londoner said he had registered two days ago and was unable to get through on the phone line as it appeared to be constantly engaged. A supermarket owner from Coventry who travelled to Afghanistan two months ago to try to process passport applications for three of his children who are eligible to become UK citizens said he was frustrated at a lack of clear advice from the Foreign Office. “I emailed about 10 days ago saying I’m a British citizen and I’m stuck in Kabul with my family. Since then I’ve only had two emails from them: one saying that they have received my email and are working on it, and another saying avoid the airport because the airport is in danger. Then nothing else,” he said. The man said he was getting daily calls from about 15 other British nationals also stuck in the capital, asking what he was planning to do. He had emailed his MP but got an automated response. “I’m just hoping they can clarify whether I can bring my kids out. Then I will try to find a way, slowly when the situation is better, to go to Pakistan or Tajikistan and then fly to Dubai and then back to England,” he said. A Foreign Office spokesperson said: “The UK and international partners are all committed to ensuring that our citizens, nationals and residents, employees, Afghans who have worked with us and those who are at risk can continue to travel freely to destinations outside Afghanistan. We have been clear that the Taliban must allow safe passage for those who want to leave.”