Turkey's prime minister has called a suicide blast at Ataturk Airport in Istanbul a "heinous planned attack" as the Foreign Office said it was "urgently seeking further information" about possible British casualties.
More than 36 people have been killed and a further 147 wounded in the attack and reports have suggested those figures are set to rise. Here's what we know so far.
How was the attack carried out?
Three suicide bombers arrived at the entrance of Ataturk Airport in Istanbul in a taxi and detonated explosives after they had opened fire.
IS suspected to have carried out the attack
Turkish prime minister Binali Yildirim has said: "The findings of our security forces point at the Daesh organisation as the perpetrators of this terror attack," he said. "Even though the indications suggest Daesh, our investigations are continuing."
Turkish president Recep Tayyip Erdogan said the attack, which took place during the Muslim holy month of Ramadan, "shows that terrorism strikes with no regard to faith and values".
Calling on the international community to take a firm stand against terrorism, he said: "Turkey has the power, determination and capacity to continue the fight against terrorism until the end."
IS has not claimed responsibility for the attack.
Foreign nationals among the victims
Yildirim has said there are foreigners are among the victims and called for "global co-operation" in tackling terrorism.
Defence Secretary Philip Hammond described himself as "shocked" by the incident and said "we stand ready to help".
A Foreign Office spokesman said: "We are in close contact with authorities in Istanbul and urgently seeking further information following an incident at Ataturk Airport. Our staff in Istanbul and London stand ready to support any British nationals affected."
Prime Minister David Cameron's reaction from Brussels
David Cameron described the terrorist attack as "hideous".
Cameron, in Brussels for what is likely to be his final EU summit meeting with fellow leaders, said the UK would continue to work with the other countries after Brexit on "keeping our countries safe, keeping our people safe - and it's particularly important to say that tonight again when there has been another hideous terrorist attack in Turkey".
Eyewitness Will Carter who was inside the terminal, said he heard explosions. Speaking to Radio 5Live he said: "I saw a fireball and some of the ceiling came down - just before there was panic and people running."
BBC correspondent Mark Lowen was grounded on the runway after landing at the airport and said he was held on the tarmac for around four hours before being allowed off the aircraft and into the terminal.
Reporting from the scene he said: "You can see how chaotic the situation is here. Huge crowds of people are trying to get into the terminal building."
Flights have resumed at Ataturk airport
Flights in and out of the airport, which is one of the busiest in the world, were suspended after the attack but Yildirim said air traffic had now resumed.
Turkey has been targeted by terrorists in recent months
Turkey has suffered several deadly attacks in recent months which have been blamed on Kurdish separatists or IS. Several of the bombings targeted areas popular with tourists while another attack on a military barracks in Ankara killed 28 people.
The latest attack comes just months after Brussels was hit by suicide bombings at the airport and on the Metro. IS claimed responsibility for the attacks on March 22, which killed 32 and wounded another 270.