The Taliban has condemned the bombing outside Kabul airport and said that it happened in an area controlled by US forces.

Initial reports stated that a twin suicide bomb attack killed at least 13 people outside Kabul airport on Thursday. According to Reuters, a Taliban official said that the deceased include children.

The news of the explosions was confirmed by the Pentagon. Scores of people had gathered at the Kabul airport to flee the country as part of evacuation operations of several countries triggered by Taliban's takeover of Afghanistan earlier this month.

Earlier, the UK and several other countries had warned of a possible terror attack on Kabul's airport. 

Also read: Kabul suicide attack: At least 13 dead, several injured

Several countries had urged their citizens to avoid the airport, where an official said that there was threat of a suicide bombing. But with days left for evacuation efforts to end, few appeared to heed the warnings.

It is reportedly said that the explosion went off in a crowd of people waiting to enter the airport.

CNN News reported that three US officials and a source familiar with the situation said that there were some US personnel among the casualties.

Also read: India evacuates 35 more people from Kabul

Pentagon spokesman John Kirby posted a tweet that read, "We can confirm that the explosion at the Abbey Gate was the result of a complex attack that resulted in a number of US & civilian casualties. We can also confirm at least one other explosion at or near the Baron Hotel, a short distance from Abbey Gate. We will continue to update."

According to three US officials, the blast took place at one of the entry gates of the Hamid Karzai International Airport and appears to be a suicide attack.

Meanwhile, the US Embassy in Kabul said that US citizens who were at the Abbey Gate, East Gate, or North Gate of the airport "should leave immediately" in the wake of the blast.