United States President Joe Biden warns of another attack on Kabul Airport

Evacuees from Afghanistan who made it on the last flight to Italy. [Courtesy]

The President of the United States of America, Joe Biden, has warned of another highly likely attack on Kabul Airport.

Biden says the attack could come as early as Sunday, August 29 as the State Department urged all US citizens to leave the area near the airport because of a "specific, credible threat".

BBC has reported that evacuations by the US are still underway although the final UK troops, diplomats and officials are still left in Kabul.

On Thursday, August 26, a suicide bombing near the airport killed some 170 people.

A local branch of the Islamic State group - Islamic State in Khorasan Province (IS-K) - claimed the attack.

The Taliban condemned the airstrike, saying the Americans should have consulted them first, a spokesman told Reuters news agency.

Reports by BBC indicate that US troops have begun their withdrawal from the airport - their numbers are now down to 4,000, down from a peak of 5,800 in the past week.

The next few days are likely to be the most dangerous since the evacuation began, White House officials say.

Just over 1,000 civilians remain to be airlifted from Kabul airport, an unnamed Western official told Reuters news agency.

The Taliban have set up further layers of checkpoints around the airport and are not allowing most Afghans through, the Associated Press (AP) reports.

In all, more than 110,000 people - both Afghans and foreign nationals - have been evacuated from Kabul airport since the airlift began two weeks ago.

On Saturday, Italy's final flight from Afghanistan arrived in Rome. Italy said it had evacuated almost 5,000 Afghan citizens from Kabul - the highest number of any EU country.

France said it had flown out more than 2,800 since 17 August, while Germany said it had taken about 4,000 Afghans.

The head of the UK's armed forces, General Sir Nick Carter, said it was "heartbreaking" that they had not been able to rescue everyone.

With the possibility of leaving by air now dwindling, many Afghans are reportedly now trying to escape the country via the land border with Pakistan, to the east.

The border gates near the southern town of Spin Boldak are open and some people have been making it through. One of the main border crossings, at Torkham, is closed.

France and Britain will urge the UN to create a "safe zone" in Kabul to help evacuation efforts, French President Emmanuel Macron said.

He said it would allow the international community to carry out humanitarian work and "maintain pressure on the Taliban".

Since the Taliban took Kabul on 15 August, the Afghan economy has been in freefall as aid donors freeze funds and panicked depositors seek to withdraw their money from banks.

On Saturday crowds of protesters gathered outside banks in the Afghan capital.

"If the situation continues and employees of the government don't get their salaries and a businessman cannot get his money from the bank for trading, the result of this is very horrible, and there will be poverty in the society as well, and no one can solve that issue," one man told Reuters.