Two powerful bomb blasts have struck the perimeter of Kabul's Hamid Karzai International Airport, as civilians continued to seek to escape on flights from Taliban-controlled Afghanistan.

At least 90 people have been killed and 150 others wounded, a senior health official in Kabul told the BBC.

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 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.

Reports say the second explosion took place near a sewage canal where Afghans were waiting to be processed, close to the gate, and that some victims were blown into the water.

A US official said that at least one attacker had been wearing an explosive vest.

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".

They have been rising all day.

The final number of US and Afghan - including Taliban - casualties remains unconfirmed.

But the Pentagon said that 13 US military personnel had been killed and 15 injured. A senior health official in Kabul told the BBC that at least 90 people had died, and 150 were injured.

Images being shared on social media show the injured being taken away in wheelbarrows.

Huge crowds had been gathering in the area, hoping to be accepted on to an evacuation flight.

The attack is likely to significantly complicate the effort to airlift thousands of people out of Afghanistan.

Before the attack, a number of countries including Germany, the Netherlands and Canada, had announced that they could no longer conduct flights.

Turkey has announced that its troops, who had been providing security at the airport for six years, were withdrawing.

Graphics by Prina Shah and Gerry Fletcher