A RAAF C-130 Hercules successfully evacuated 26 people from Kabul airport to the United Arab Emirates where the Australian military is based for the operation.

The evacuees will then be transferred to Australia.

Prime Minister Scott Morrison said efforts to extract Australians and Afghans who helped allied forces over the past two decades would ramp up in subsequent flights.

“This is not a simple process,” he told reporters in Canberra.

Regular flights are scheduled in coming days but poor weather forecast may hamper evacuation efforts.

Morrison concedes not all Afghans who helped Australia will be rescued as part of the operation.

US Deputy Secretary of State Wendy Sherman says the US has seen reports that the Taliban are preventing civilians from reaching the besieged airport.

Sherman made the remarks at a news briefing in Washington, where she said in the last 24 hours US military flights had evacuated more than 2000 people.

Earlier on Wednesday, US troops guarding the evacuation effort at Kabul airport said they had fired shots in the air in an effort to control the desperate scenes.

The Taliban said their soldiers had also fired shots in an attempt to disperse crowds.

The number of US troops at Kabul’s international airport reached about 4500 on Wednesday and several hundred more were expected over the next 24 hours.

Australia will provide 3000 humanitarian visas this financial year to Afghan refugees desperately trying to flee the Taliban.

That will come from the existing intake, rather than a special allocation, and is below other nations’ commitments.

Canada has offered resettlement to more than 20,000 people at risk and the United States is accelerating its visa application process.

Australia has been accepting between 1300 and 1900 Afghans on humanitarian grounds in recent years.

-with AAP