A series of deadly explosions tore through crowds at Istanbul's Atatrk international airport on Tuesday evening, leaving at least 36 people dead and scores more injured in an attack officials blamed on the Islamic State terror group.

Shortly before the blasts, assailants armed with AK-47 rifles exchanged gunfire with security guards outside the airport's international terminal, according to officials.

The gunmen then detonated what are believed to have been suicide bombs. Three attackers died on the scene, said the Turkish prime minister, Binali Yldrm.

Five of the dead were police officers, according to the Turkish national broadcaster TRT, which reported that at least 147 people were injured in the attack.

In a press conference in Istanbul on Tuesday night, Yldrm said: "No matter where the terror comes from, our country is strong enough to fight against this terror. I call on every citizen to act in unity and stand by each other."

He said that by 2.22 am local time air traffic was "back to normal and flights are resumed".

Some foreigners were among the victims, he said.

A witness told Reuters that before the explosions one of the gunmen opened fire at random as he walked through the terminal.

Roads around the airport were sealed off for regular traffic after the attack and several ambulances could be seen driving back and forth. Hundreds of passengers were flooding out of the airport and others were sitting on the grass, their bodies lit by the flashing lights of the emergency vehicles.

South African Judy Favish, who spent two days in Istanbul as a layover on her way home from Dublin, had just checked in when she heard an explosion followed by gunfire and a loud bang.

She said she hid under the counter for some time.

Favish said passengers were ushered to a cafeteria at the basement level where they were kept for more than an hour before being allowed outside.

Another Turkish official said attackers detonated explosives at the entrance of the international terminal after police fired at them.

The official, who spoke on condition of anonymity in line with government protocol, said the attackers blew themselves up before entering the x-ray security check at the airport entrance.

Turkish airports have security checks at both the entrance of terminal buildings and then later before entry to departure gates.

The private DHA news agency said the wounded, among them police officers, were being transferred to Bakirkoy State Hospital.

Turkey has suffered several bombings in recent months linked to Kurdish or Islamic State group militants.

The bombings include two in Istanbul targeting tourists - which the authorities have blamed on the Islamic State group.

The attacks have increased in scale and frequency, scaring off tourists and hurting the economy, which relies heavily on tourism revenue.

Istanbul's Ataturk Airport was the 11th busiest airport in the world last year, with 61.8 million passengers, according to Airports Council International. It is also one of the fastest-growing airports in the world, seeing 9.2 percent more passengers last year than in 2014.

White House spokesman Josh Earnest said the United States condemns in the strongest terms possible the attacks at the Istanbul Ataturk Airport. Earnest said the US sends its deepest condolences.

The US remains steadfast in its support for Turkey, a NATO ally and partner, Earnest said, "along with all of our friends and allies around the world, as we continue to confront the threat of terrorism."