A RAAF C-130 Hercules flight has been able to land in Kabul as Australia’s rescue mission for hundreds of people from Afghanistan begins.

The evacuation operation, which involves 250 troops and three RAAF aircraft, began with a military transport plane flying out of Kabul on Wednesday morning.

Sources in the embattled city told the ABC that Australians were told to head to the city’s airport late on Tuesday.

Australia’s forces are hoping to get as many as 600 people out of the Afghan capital. Later on Wednesday, Prime Minister Scott Morrison said there were 26 people on board the Hercules – including Australian citizens, Afghan nationals with visas and one foreign official working in an international agency – when it landed back in the United Arab Emirates just before 11am Canberra time.

“I can confirm that security situation at the airport has improved, and more broadly across Kabul, and that is supported particularly by the presence of US and UK troops on the ground being able to take control of the airport,” he said.

“It still, though, remains an incredibly challenging environment in which to operate.”

Reports of the dangerous mission came after Mr Morrison said earlier that some Afghans who helped Australia were likely to be left behind when rescue flights departed Taliban-controlled Kabul.

He issued a direct message to veterans who have been pleading with the federal government to bring more interpreters and other staff to Australia.

“We will continue to do everything we can for those who have stood with us, as we have to this day,” he said in Canberra on Tuesday.

“But, I want to talk openly to veterans that, despite our best efforts, I know that support won’t reach all that it should.”

Thousands are trying to flee Kabul after the Taliban’s arrival.

Cabinet’s national security committee is meeting daily to discuss plans to extract Australians and Afghans who helped allied forces during the two-decade war.

There are grave concerns the Taliban will hunt down and execute people who helped Australia, the United States and other allies.

Since April, 430 Afghan nationals who have worked with Australia have been allowed into the country, with a total of 1800 granted visas.

There are more than 130 Australians working for the United Nations, non-government organisations and elsewhere still in Afghanistan, which is now under Taliban control.

Home Affairs Minister Karen Andrews expected the vast majority of people applying for temporary visas would be approved.

“I’m hopeful there is only a very, very small number, that may require significant security checking,” she told 4BC radio.

People swarmed Kabul airport in an attempt to board military flights, with footage showing some falling to their deaths after clinging to planes.

NATO video posted online on Tuesday showed the runway empty with American troops on the tarmac.

Immigration Minister Alex Hawke confirmed no Afghan visa holder in Australia would be sent home while the situation remained dire.

Mr Morrison refused to commit to offering paths to permanent residency or citizenship, but insisted there were no plans to send people into danger.

Opposition Leader Anthony Albanese said the idea that minority groups like the Hazara community would ever return wasn’t realistic.

“We need to give them the certainty of Australian citizenship on a permanent basis, rather than some pretence that somehow their circumstances are temporary,” he said.

Mr Morrison didn’t rule out a special intake of refugees, similar to the 12,000 people granted asylum from Syria in 2015.

But he said his immediate focus was on making sure the Australian mission was successful given the desperate situation in Kabul.

-with AAP