Two powerful bomb blasts struck the perimeter of Kabul's Hamid Karzai International Airport on Thursday, as civilians continued to seek to escape on flights from Taliban-controlled Afghanistan.
At least 90 people were killed and 150 others wounded.
The Pentagon confirmed 13 US service personnel were among those killed.
The bombings came hours after Western governments had warned their citizens to stay away from the airport, because of an imminent threat of an attack by IS-K, the Afghanistan branch of the Islamic State group.
Here is what we know about what happened.
The blasts happened outside airport
The first explosion happened at about 18:00 local time (13:30 GMT), close to the Baron Hotel, near the airport's perimeter.
The hotel was being used by British officials to process Afghans hoping to travel to the UK.
It was followed by gunfire and then a second explosion close to the Abbey Gate, one of the airport's main entrances.
UK Defence Secretary Ben Wallace said a suicide bomber walked into the middle of families waiting outside the gate before carrying out the attack.
He told the BBC: "We think it was a suicide vest and a smaller device. The individual got to the perimeter we had pushed out the day before in response to that threat.
"It was about 300 metres, we think, from the Baron's hotel, and [the bomber] walked straight into the middle of those families waiting."
Reports say some victims were blown into a sewage canal where Afghans were waiting to be processed.
Many of the victims of the attack were rushed to Kabul's Emergency Hospital.
US and British troops had recently been deployed to guard the area around the Abbey Gate.
According to one account, one attacker fired into a crowd of people, although reports also said Taliban guards had fired into the air.
US citizens who had gone to the area around the airport had been warned before the attack to "leave immediately".
Casualty figures
It's believed some 90 people were killed and 150 injured.
The Pentagon said that 13 US military personnel, including US marines and a US Navy medic, were among the dead. A further US 15 troops were injured.
Images taken at the scene showed the injured being taken away in wheelbarrows.
Huge crowds had been gathering in the area, hoping to be accepted on to an evacuation flight.
Some countries had already ended their evacuation flights
The attack is likely to significantly complicate the final effort to airlift thousands of people out of Afghanistan ahead of 31 August.
Before the attack, a number of countries including Germany, the Netherlands and Canada, had announced that they could no longer conduct flights.
Turkey also announced that its troops, who had been providing security at the airport for six years, were withdrawing.
The UK has confirmed that it will no longer be calling people forward to the airport for evacuation flights.
Graphics by Prina Shah and Gerry Fletcher