"We do not believe that there was a second explosion at or near the Baron hotel, that it was one suicide bomber," General Hank Taylor said.

It had been believed there was a second blast at that hotel near the airport.

The attack Thursday killed at least 85 people, including 13 US troops, and opened up a deadly new chapter in the drama unfolding at Kabul airport, as thousands of people fearing Taliban rule try to escape their own country in a frantic US-led airlift due to conclude on August 31.

The Pentagon also said the evacuation drive could be hit with more attacks like the one Thursday, which was claimed by the local arm of the Islamic State group.

"We still believe there are credible threats... specific, credible threats," said US military spokesman John Kirby.

With more than 100,000 people spirited out of Afghanistan since August 14 as part of the airlift, Taylor said 5,400 more are still at the airport awaiting evacuation.

He said the United States will be able to airlift people out "until the very last moment."