The threat comes from an ISIS affiliate in Afghanistan known as ISIS-K, Islamic State of Iraq and the Levant – Khorasan Province, reports Daily Mail.

ISIS announced its expansion to the Khorasan region in 2015, which historically encompasses parts of modern day Iran, Central Asia, Afghanistan, and Pakistan, read the newspaper report.

The officials told Daily Mail that the security situation around the airport had significantly deteriorated in recent days, given the new terror threats, and contributed to Biden's decision not to declare an extension of the August 31 deadline for all U.S. troops to leave.

ISIS-K is targeting airport gates - which have seen thousands of people gather in a bid to flee - as well as military and commercial aircraft evacuating people from the capital city, the sources told Politico as quoted by the British newspaper.

President Joe Biden himself had warned about ISIS attack risks in future.

He was quoted as saying by a statement issued by the White House: " The longer we stay, starting with the acute and growing risk of an attack by a terrorist group known as ISIS-K, an ISIS affiliate in Afghanistan — which is the sworn enemy of the Taliban as well — every day we’re on the ground is another day we know that ISIS-K is seeking to target the airport and attack both U.S. and Allied forces and innocent civilians."