Warning: Distressing content

The Taliban is reportedly blocking people from boarding rescue flights out of Kabul airport, shooting at the crowd and throwing gas bombs as people try to get out of Afghanistan.

The ABC's Stephen Dziedzic tweeted that he had spoken to a number of Australians who say it is "impossible" to get through and they called on the Morrison Government to do something to help.

Unconfirmed reports on social media say some people have been killed as US forces and the Taliban struggle to contain the desperate throngs on their respective sides of an unofficial no-man's land.

"I went to the airport with my kids and family … the Taliban and Americans were shooting," one man, who until recently had worked for a foreign NGO, told AFP.

"Despite that, people were still moving forward [to get in] because they knew a situation worse than death awaited them outside the airport."

There have been chaotic scenes since the weekend when the Taliban drove unopposed into the capital after a two-week lightning offensive that capped a simmering 20-year insurgency.

Twelve people have been killed in and around the airport since Sunday, a Nato and a Taliban official said. The deaths were caused either by gunshots or by stampedes, the Taliban official said.

He urged people who did not have the legal right to travel to go home.

"We don't want to hurt anyone at the airport," said the Taliban official, who declined to be identified.

An NZDF plane on a mercy dash to rescue New Zealanders, interpreters and others who worked with Kiwi troops fighting the Taliban left yesterday morning.

It was confirmed that the RNZAF C-130 Hercules aircraft would touch down at Kabul's Hamid Karzai International Airport.

The emergency evacuation contingent amounts to around 80 people, including aircrew and maintenance staff, a medical team, operational support staff, logistics personnel and force protection. The NZDF would not confirm whether any special forces operatives were on board.

The deployment could last for up to a month.

Australia's Foreign Affairs Minister Marise Payne said the government was aware of Australians having access issues to the airport in Kabul.

A Taliban fighter at Kabul airport.

"We absolutely know there are continuing, significant issues ongoing with access to Hamid Karzai International Airport and we have seen the reports of those," she said.

"We're also working with other countries now to share lists of potential passengers and to co-ordinate our information and rescue efforts as we are able to," she said.

"We're working with our counterparts to ensure that we have a staging area, a designated space, at Hamid Karzai International Airport and also transporting supplies to support that.

"We are continuing to contact those Australians and visa holders, and to support them where we are able to, to get through those checkpoints and into the airport."

The United States said the Taliban were reneging on pledges to allow Afghans who worked with the United States and its allies out of the country.

"We have seen reports that the Taliban, contrary to their public statements and their commitments to our government, are blocking Afghans who wish to leave the country from reaching the airport," Deputy Secretary of State Wendy Sherman told reporters.

"We expect them to allow all American citizens, all third-country nationals and all Afghans who wish to leave to do so safely and without harassment."

Taliban spokesman Zabihullah Mujahid said on Tuesday that the new regime would be "positively different" from the 1996-2001 regime.

But Taliban 2.0 remains a hard sell, with women largely staying off the streets, and journalists and those who have worked with Western governments and organisations saying they are terrified.

Memories of the militants' brutal 1996-2001 regime and the near-two-decade insurgency that killed tens of thousands are etched on Afghan minds – especially those of women and religious minorities.

As many as 15,000 American citizens may remain inside Afghanistan, US President Joe Biden has said.

Meanwhile, there were heartbreaking scenes as Afghan mothers passed their children over walls and barbed wire to get them to safety.

"It was terrible, women were throwing their babies over the razor wire, asking British soldiers to take them, some got caught in the wire," a British officer told Sky News.

- Matthew Murphy, news.com.au