The Taliban has deployed extra forces around Kabul's airport to prevent large crowds from gathering after a devastating suicide attack two days earlier, as the massive US-led airlift winds down ahead of its August 31 deadline.

New checkpoints have appeared on roads leading to the airport, some manned by uniformed Taliban fighters with Humvees and night-vision goggles captured from Afghan security forces.

It comes as Joe Biden said another terrorist attack on Kabul's airport is "highly likely in the next 24-36 hours"

The US Embassy in Kabul issued a security alert saying "Due to a specific, credible threat, all U.S. citizens in the vicinity of Kabul airport (HKIA), including the South (Airport Circle) gate, the new Ministry of the Interior, and the gate near the Panjshir Petrol station on the northwest side of the airport, should leave the airport area immediately."

Areas where large crowds of people had gathered over the past two weeks in the hope of fleeing the country following the Taliban takeover are now largely empty.

A suicide attack on Thursday by an affiliate of so-called Islamic State (Isis-K) killed 169 Afghans and 13 US service members, and there are concerns that the group, which is far more radical than the Taliban, could strike again.

Many western nations have completed their evacuation operations ahead of Tuesday's deadline for the withdrawal of all US forces.

Sources in Kabul said Taliban personnel claimed to have been told by the Americans to only let US passport-holders through a final checkpoint close to the airport.

On Saturday, the Taliban fired warning shots and deployed some coloured smoke on a road leading to the airport, sending dozens of people scattering, according to a video circulating online.

Earlier on Saturday, the US military struck back at IS, bombing one member in Afghanistan less than 48 hours after the Kabul suicide bombing.

US central command said it carried out a drone strike against an IS member in Nangarhar believed to be involved in planning attacks against the US in Kabul. The strike killed one individual, and spokesman Capt William Urban said there were no known civilian casualties.

It is not clear if the individual killed in the strike was involved specifically in Thursday's attack.

Meanwhile, hundreds of Afghans protested outside a bank in Kabul and others formed long queues at cash machines, as a UN agency warned a worsening drought could leave millions of people in need of humanitarian aid.

The economic crisis, which predates the Taliban takeover earlier this month, could give western nations leverage as they urge Afghanistan's new rulers to form a moderate, inclusive government and allow people to leave after the planned withdrawal of US forces on August 31.

Afghanistan is heavily dependent on international aid, which covered around 75% of the western-backed government's budget.

The Taliban has said it wants good relations with the international community and has promised a more moderate form of Islamic rule than when it last governed the country, but many Afghans are deeply sceptical.

The protesters at New Kabul Bank included many civil servants demanding their salaries, which they said had not been paid for the past three to six months.

They said even though banks reopened three days ago, no-one has been able to withdraw cash. ATM machines are still operating, but withdrawals are limited to around 200 dollars (£145) every 24 hours, contributing to the formation of long queues.

The Taliban cannot access any of the central bank's nine billion dollars (£6.5 billion) in reserves, most of which is held by the New York Federal Reserve.

The International Monetary Fund has also suspended the transfer of some 450 million dollars (£327 million). Without a regular supply of US dollars, the local currency is at risk of collapse, which could send the price of basic goods soaring.

Meanwhile, a UN agency has warned that a worsening drought threatens the livelihoods of more than seven million people.

The Rome-based Food and Agriculture Organisation (FAO) said Afghans are also suffering from the coronavirus pandemic and displacement from the recent fighting.

Earlier this month, the United Nations World Food Programme estimated that some 14 million people - roughly one out of every three Afghans - urgently need food assistance.

The FAO said crucial help is needed ahead of the winter wheat planting season, which begins in a month in many areas.

So far, funding would cover assistance to only 110,000 families of farmers, while some 1.5 million need help, the agency said, adding that the current harvest is expected to be 20% below last year's.

US president Joe Biden has said he will adhere to a self-imposed August 31 deadline for withdrawing all American forces.

The Taliban, which controls nearly the entire country outside Kabul's airport, has rejected any extension.

Italy said its final evacuation flight had landed in Rome but that it would work with the UN and countries bordering Afghanistan to continue helping Afghans who had worked with its military contingent to leave the country.

"Our imperative must be to not abandon the Afghan people," especially women and children, Italian foreign minister Luigi Di Maio said.

He added that 4,890 Afghans were evacuated by Italy's air force on 87 flights, but did not say how many others were still eligible.

More than 100,000 people have been safely evacuated through the Kabul airport, according to the US.

The Taliban has encouraged Afghans to stay in the country, pledging amnesty even to those who fought against them. The militants have said commercial flights will resume after the US withdrawal, but it is unclear if airlines will be willing to offer service.

The US and its allies have said they will continue providing humanitarian aid through the UN and other partners, but any broader engagement - including development assistance - is likely to hinge on whether the Taliban delivers on its promises of more moderate rule.

When the Taliban last governed Afghanistan, from 1996 until the US-led invasion in 2001, it imposed a harsh interpretation of Islamic law.

Women were largely confined to their homes, television and music were banned, and suspected criminals were maimed or executed in public.

This time, the Taliban says women will be allowed to attend school and work outside the home. It has been negotiating with senior Afghan officials from previous governments and says it wants an "inclusive, Islamic government".

But even as the group's top leadership struck a more moderate tone, there have been reports of human rights abuses in areas under Taliban control. It is unclear whether fighters are acting under orders or on their own.