Kabul attack: Biden vows revenge as dozens killed in twin airport blasts including 13 Americans

• Two bombs have exploded outside Kabul airport

• At least one was a suicide attack

• Full extent of death toll remains unknown

• Pentagon confirms 13 US troops killed, and more injured

• Some reports say at least 60 Afghans have been killed

• Terror group Isis-K claims responsibility for attack

• Ministry of Defence say so far there have been no British casualties

Terrorists have struck the crowded gates of Kabul airport in a twin bomb blast that has killed dozens of people including children and at least 13 Americans.

There is no complete death toll from at least two explosions, but video images uploaded by Afghan journalists showed dozens of bodies killed in tightly packed crowds outside the airport.

Isis-K, an affiliate of the so-called Islamic State in Afghanistan, has claimed responsibility for the attack. US officials also blamed the group

The Pentagon has confirmed 13 US service members have been killed. The BBC has reported at least 60 deaths and 140 wounded, citing an Afghan health official. At least 140 are believed to be injured.

Joe Biden said in a televised address that the US would "hunt down" those responsible. "We will not forgive, we will not forget, we will hunt you down and make you pay."

He promised US evacuations would continue and gave no indication of a change in next Tuesday's pullout deadline.

Several Western countries said the airlift of civilians was now effectively over, with the United States having sealed the gates of the airport leaving no way out for tens of thousands of Afghans who worked for the West through two decades of war.

Both explosions took place near the Abbey Gate entrance to the airport, where large numbers of refugees have gathered in recent days trying to flee the Taliban. The first is believed to have been a suicide bomber. The second explosion, near the Baron Hotel, was accompanied by gunfire.

A watery ditch by the airport fence was filled with bloodsoaked corpses, some being fished out and laid in heaps on the canal side while civilians searched for loved ones.

"For a moment I thought my eardrums were blasted and I lost my sense of hearing. I saw bodies and body parts flying in the air like a tornado blowing plastic bags. I saw bodies, body parts elders and injured men, women and children scattered in the blast site," said one Afghan who had been trying to reach the airport

"Bodies and injured were lying on the road and the sewage canal. That little water flowing in the sewage canal had turned into blood."

Boris Johnson said the UK will continue to work "flat out" evacuating as many as possible despite the “barbaric” terrorist attack at Kabul airport.

He said members of the US military “very sadly have lost their lives” in the attacks in Kabul, as well as “many Afghan casualties.”

Read more: Who are ISIS-K? What we know about the terror group 'behind deadly attack' in Kabul

Around 60 people wounded in the attack on Kabul airport on Thursday are being treated at a nearby surgical centre, according to Emergency, a charity that runs a network of war hospitals and first aid posts across Afghanistan.

The Ministry of Defence said: "There have been no reported UK military or UK Government casualties following the incidents in Kabul."

The Pentagon said: "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 Afghan journalist Bilal Sarwary, an eyewitness told him that one of the explosions took place when a suicide bomber blew himself up in the middle of a large crowd near a sewage canal where Afghans had gathered to have their documents vetted.

Read more: Council stops taking donations for Afghan refugees after being ‘overwhelmed’

Witnesses have described the chaos, with one former Royal Marine saying his vehicle was targeted by a gunman.

Paul Farthing, known as Pen, who founded the Nowzad shelter in Kabul, is aiming to get 200 dogs and cats out of the country alongside his animal shelter staff, said: “We’re fine but everything is chaos here.

“All of a sudden we heard gunshots and our vehicle was targeted, had our driver not turned around he would have been shot in the head by a man with an AK-47."

Thousands of people have thronged around the airport in recent days as they try to board evacuation flights out of Afghanistan.

Tory MP Nus Ghani said she was on the phone to somebody outside Kabul airport when the explosion happened.

The Wealden MP tweeted: "Explosion at Kabul airport. I was on the phone to an Afghan outside the airport when he heard the explosion.

"Praying that he gets away safely and we get his family safe passage out of this nightmare."

Additional reporting by Reuters

Watch: Afghanistan: Boris Johnson says time remaining for Kabul evacuations is 'quite short' but 'overwhelming majority' of people have left