The US embassy has urged its nationals to “avoid traveling to the airport” due to security threats.
Darlene Superville, White House reporter for AP, tweeted: “Possible IS [Islamic State] threats against Americans in Afghanistan force military to find new ways for evacuees to reach Kabul airport.”
A CBS News reporter added: “A former Afghan interpreter who tried to get into the airport today – for the fifth time- said Taliban outside the airport told people that ISIS is planning an attack.”
John Kirby, the Pentagon press secretary, was asked by reporters whether there is an ISIS or Al-Qaeda threat.
He replied: “We’re not going to get into specific details about the threat environment.”
In a statement the US Embassy in Kabul said: “Because of potential security threats outside the gates at the Kabul airport, we are advising US citizens to avoid travelling to the airport and to avoid airport gates at this time unless you receive individual instructions from a US government representative to do so.
“US citizens requesting assistance in departing the country who have not yet completed the Repatriation Assistance Request for each traveller in their group should do so as soon as possible.
“We will contact registered US citizens as the security situation changes to provide further instructions.”
Kabul airport saw another day of chaos on Saturday, with thousands of Afghans crowding outside hoping to leave.
Western powers are evacuating their nationals and Afghan allies, but the number of people present makes any operation difficult.
Sky News reports several people were crushed to death in the crowd on Saturday.
ISIS has an established presence in Afghanistan, with its Islamic State-Khorasan Province affiliate.
It has fought bloody battles against both Afghan security forces and the Taliban, with captured Taliban militants beheaded by ISIS fighters.
According to the Wall Street Journal the Taliban executed the leader of ISIS in Afghanistan, Abu Omar Khorasani, shortly after the fall of Kabul.
He was being held as a prisoner by the Afghan government, until the Taliban overran the prison.
In 2015 the BBC reported the Taliban were sending 1,000 of their special forces troops to crush ISIS in Afghanistan.
The group had established a presence in the provinces of Nangarhar, Farah, Helmand and Zabul.
More to follow…