Earlier Friday, the Pentagon said that the high-risk Kabul airlift operation to evacuate Americans and Afghan allies still faced “specific, credible threats”.

“US citizens who are at the Abbey gate, East gate, North gate or the New Ministry of Interior gate now should leave immediately,” the US Embassy in Kabul said in a security alert.

“Because of security threats at the Kabul airport, we continue to advise US citizens to avoid travelling to the airport and to avoid airport gates,” the embassy said.

The alert gave no further details on what the security threats might be, but it followed Thursday’s attack that killed scores of people including 13 US servicemen.

The blast claimed by the Islamic State group targeted US forces, but hit hardest the mass of people who had converged on the airport in a desperate bid to escape the Taliban’s feared hardline rule.