America has launched emergency airlifts for Afghans who worked with its armed forces and diplomats, evacuating hundreds who are still waiting for their visas to the United States on military flights.

Only people in the final stages of a long, slow and bureaucratic visa process are eligible for the airlift, but bringing applicants to the continental US in large numbers is still unprecedented in recent years, officials working on the programme say.

It reflects growing political pressure in the US over the fate of Afghans who supported the Nato mission in Afghanistan and now face retaliation as the security situation deteriorates.

Tens of thousands of Afghans with a US connection are waiting for a response to their visa applications, including more than 18,000 who worked for the military or embassy, and in excess of 50,000 family members eligible to travel with them. Some have been in limbo for years.

There is increasing concern about the fate of Afghan allies in the UK too. Dozens of former military commanders last week called on the government to allow more people who worked for British forces to settle in the country.

Last week CNN reported that a former interpreter for American troops had been beheaded by Taliban fighters at a militant checkpoint. Others still in the country say they face regular death threats and fear they will be hunted down as the insurgents seize more territory.

The Taliban’s sweeping gains, in a campaign launched in May, have so far been confined to rural areas, but government troops and militias that back them have been struggling to hold back Taliban fighters inside three provincial capitals.

In the south, airstrikes were called in to protect Lashkar Gah in Helmand and Kandahar City, while in western Herat, fighting closed the airport for several days and the UN said its compound came under attack by militants who killed a guard.

The first evacuation flight to America landed on Thursday, with about 200 passengers from Kabul, said JC Hendrickson, senior director for policy and advocacy at the International Rescue Committee (IRC), which is supporting the new arrivals. In a sign of how hastily the programme has been set up, Hendrickson said they were only asked to take part last week and rushed staff to Virginia to prepare.

The IRC has helped more than 16,000 Afghans settle in the US after securing special immigrant visas (SIVs), but this is the first time they have been involved with visa processing. They expect up to 3,000 people to arrive on the special flights.

“Certainly in the last decade or two, I’ve never heard of anything like this … in the territorial United States,” Hendrickson said.

“It’s a big step in the right direction, supporting people whose lives are at risk because of their affiliation with the United States.”

He called on the government to go further in supporting Afghans at risk, including clearing the backlog of SIV applications, and setting up a separate visa programme for Afghans who have American links that could make them Taliban targets, but do not qualify for an SIV visa.

“The government should take an ‘everything and the kitchen sink’ approach to helping people who are US-affiliated,” Hendrickson said, praising moves in Congress to allocate additional resources to processing visas for military and embassy staff, and create a visa pathway for other Afghans at risk. “There are tools that the US government can can deploy outside of this specific (SIV) process. And we think it’s urgently necessary that they do so.”

President Biden has promised that the US will not abandon allies in Afghanistan, as it did during its hasty exit from Vietnam.

The government is scrambling around for ways to get the tens of thousands of visa applicants to safety, while they are still being vetted, and is reportedly in talks with governments in Central Asia and the Persian Gulf about hosting them.

Those being allowed directly into the US, under a condition known as “humanitarian parole”, are the small proportion who had already completed strict background and security vetting. They were only waiting for medical checks, or for visas to be issued.

Normally people who secure SIV visas are expected to arrange their own travel from Afghanistan, but military planes have flown this group to the US. They will be housed on the Fort Lee military base until they have completed the final stages of visa applications, the Pentagon said last week.

The Taliban have said they will not harm interpreters but few of those who served with the US military trust that assurance. There have been multiple reports of human rights abuses, including targeted killings, in areas seized by the group.

These include video that appeared to show Taliban fighters executing a group of commandos as they tried to surrender in May. The Taliban deny executing the soldiers and say the video was faked.

Last month militants also mutilated the body of Pulitzer prize-winning photographer Danish Siddiqui, who worked for the Reuters news agency, the New York Times reported on Saturday, citing photographs as well as Afghan and Indian officials.