Turkey has observed a national day of mourning after a gun and suicide bomb attack on Istanbul's Ataturk airport killed 42 people, including 13 foreign nationals.

Three attackers arrived in a taxi and began firing at the terminal entrance late on Tuesday. They blew themselves up after police fired back.

Officials earlier said 239 people were injured, with 41 in intensive care.

PM Binali Yildirim said early signs pointed to so-called Islamic State.

CIA Director John Brennan also said it "bears the hallmarks" of the jihadist group.

However, no-one has so far admitted carrying out the attack.

Turkish investigators are examining CCTV footage, witness statements and mobile phone video recorded by terrified passengers to try to determine the identity of the attackers.

Authorities have suggested that they were foreign nationals but this has not been confirmed.

Mr Yildirim said one of the attackers blew himself up outside the terminal, while the other two detonated explosives inside, the Associated Press news agency reports.

Footage on social media shows one moving through the building as people around him flee. He is shot by police and remains on the ground for about 20 seconds before blowing himself up.

Turkish Health Minister Recep Akdag said earlier that 128 people remained in hospital, including nationals of Saudi Arabia, Afghanistan, Pakistan, Uzbekistan, Ukraine and Switzerland.

Turkish media say 42 people were killed, with a cafe worker dying late on Wednesday. Thirteen of those who died were foreign or dual nationals.

UK Prime Minister David Cameron said there were no reports yet of any British casualties, but the Foreign Office was in contact with Turkish authorities.

Nationality of dead so far confirmed (may include dual nationality)

24 - Turkish

5 - Saudi

2 - Iraqi

1 - Chinese; Jordanian; Tunisian; Uzbek; Iranian; Ukrainian; (Palestinian ambassador to Turkey says one Palestinian woman killed)

Flights had resumed in the early morning, though with many cancellations and delays.

Turkish President Recep Tayyip Erdogan declared Wednesday a national day of mourning and said the attack should serve as a turning point in the global fight against militant groups.

Speaking later in Ankara he said that Turkey, despite being a target of "the most brutal terrorist groups", would ultimately defeat terrorism.

He added that the attackers were "not Muslims".

Analysis: Frank Gardner, BBC security correspondent

The lack of any immediate claim for this attack by so-called Islamic State is not surprising. IS rarely, if ever, claims responsibility for attacks against the Turkish state yet it is quick to advertise its assassinations of Syrian activists inside Turkey.

All the signs point towards IS being the culprits. This is what British counter-terrorism officials term "a marauding terrorist firearms attack", following a pattern first seen in the Mumbai attacks of 2008.

The Istanbul targets were international air travellers and ground staff at an iconic location, the third busiest airport in Europe.

IS is targeting Turkey because it sees its government as being un-Islamic and too close to its Western allies in Nato. IS is also feeling the pressure as the Turkish authorities move to close down its networks inside Turkey.

Turkey's other main foe, Kurdish separatists, have carried out many attacks over the years but their primary targets have tended to be Turkish policemen and soldiers.

Paul Roos, who was due to fly home to South Africa, told Reuters he saw one of the attackers.

"He was wearing all black. His face was not masked. We ducked behind a counter but I stood up and watched him. Two explosions went off shortly after one another. By that time he had stopped shooting.

"He turned around and started coming towards us. He was holding his gun inside his jacket. He looked around anxiously to see if anyone was going to stop him and then went down the escalator. We heard some more gunfire and then another explosion, and then it was over."

US President Barack Obama said: "We will not rest until we have dismantled these networks of hate that have had an impact on the entire civilised world".

Russian President Vladimir Putin offered his condolences to Turkey in a phone call with Mr Erdogan, as the pair seek to rebuild ties.

The assault on Ataturk airport - Europe's third busiest - is the sixth major attack this year targeting either Istanbul or Turkey's capital, Ankara.

The country's economy has been badly hit as a result of falling tourism.

Pope Francis denounced the "brutal terrorist attack" and the Organisation of Islamic Cooperation also condemned the "despicable terrorist act".

Ataturk airport

• Europe's third-busiest in passenger traffic after London Heathrow and Paris Charles de Gaulle, serving 61.3 million passengers in 2015. World's 11th busiest
• Opened in 1924 in the Yesilkoy area, renamed in the 1980s after the nation's first president, Mustafa Kemal Ataturk
• Two passenger terminals: one domestic, one international
• To be closed after the massive Istanbul New Airport - planned to be the largest in the world - opens in the Arnavutkoy district. Its first phase is due to be operational in 2017

Major recent attacks

2016

• 7 June, Istanbul: Car bomb kills seven police officers and four civilians. Claimed by Kurdish militant group TAK
• 19 March, Istanbul: Suicide bomb kills four people in shopping street. IS blamed
• 13 March, Ankara: Car bomb kills 35. Claimed by TAK
• 17 February, Ankara: 29 killed in attack on military buses. Claimed by TAK
• 12 January, Istanbul: 12 Germans killed by Syrian bomber in tourist area

2015

• 23 December, Istanbul: Bomb kills cleaner at Istanbul's Sabiha Gokcen airport. Claimed by TAK
• 10 October, Ankara: More than 100 killed at peace rally outside railway station. Blamed on IS
• 20 July, Suruc, near Syrian border: 34 people killed in bombing in Kurdish town. IS blamed