There were even reports of gunfire outside the airport. Those killed include civilians and US service members, the Pentagon said.

Confirming the explosions, the United States has urged its citizens to avoid travelling to the airport and asked people at the East Gate, Abbey Gate and North Gate to leave immediately.

According to reports, Taliban guards have also been wounded in the blast.

A US official told the media that the western country's service members were among the wounded.

Thousands of people have been gathering outside the Kabul airport in recent days with western troops racing to evacuate foreigners and Afghans to get out of the war-torn country by an Aug 31 deadline after the Taliban takeover of Afghanistan.

Meanwhile, another explosion took place near Baron Hotel in Kabul right after the first one.

Pentagon press secretary John Kirby confirmed about the explosions and said it was unclear if there were any casualties.

"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."

US President Joe Biden has been briefed on the explosion, said reports citing  White House officials.

Biden was in a meeting with security officials about the situation in Afghanistan when the explosion was first reported, reports added.

On August 15, the Taliban entered Kabul, prompting the US-supported civilian government to collapse.

Ashraf Ghani resigned as president and fled the country to prevent what he described as imminent bloodshed if militants had to storm the city.