A suicide gun and bomb attack on Istanbul's main airport, one of Europe's busiest, has killed at least 36 people and injured 140 more.

Three attackers were involved, with one reportedly firing a Kalashnikov as they targeted an entry point to Ataturk international airport.

The attackers blew themselves up after police fired at them, officials say.

Recent bombings in Turkey have been linked to either Kurdish separatists or the so-called Islamic State (IS) group.

This looks like a major co-ordinated assault, the BBC's Mark Lowen reports.

Ataturk airport was long seen as a vulnerable target, our Turkey correspondent adds, reporting from a plane stuck on the tarmac in Istanbul.

A Kalashnikov assault rifle was later found at the scene of the attack. Photo: Reuters

There are X-ray scanners at the entry to the terminal but security checks for cars are limited.

Turkish President Recep Tayyip Erdogan condemned the attack, calling for a "joint fight" against terrorism.

The US condemned the "heinous" attack, saying America remained "steadfast in our support for Turkey".

German Foreign Minister Frank-Walter Steinmeier said: "We grieve for the victims... We stand by Turkey".

Flights in and out of the airport were suspended after the attack.

The US Federal Aviation Administration grounded all flights between the US and Istanbul, Reuters reports.

Taxis were used to rush casualties to hospital after the attack.

Two South African tourists, Paul and Susie Roos from Cape Town, were at the airport and due to fly home at the time of the explosions.

"We came up from the arrivals to the departures, up the escalator when we heard these shots going off," Mr Roos told the Associated Press news agency.

"There was this guy going roaming around, he was dressed in black and he had a handgun."

Charles Michel, the Prime Minister of Belgium whose capital city was targeted by bombers in March, tweeted from the EU summit in Brussels: "Our thoughts are with the victims of the attacks at Istanbul's airport. We condemn these atrocious acts of violence."

In December, a blast on the tarmac at a different Istanbul airport, Sabiha Gokcen, killed a cleaner. That attack was claimed by a Kurdish group, the Kurdistan Freedom Falcons (TAK).

Security concerns and a Russian boycott over last year's downing of a Russian military jet on the Turkey-Syria border have hit the Turkish tourist sector this year.

More than 61 million passengers travelled through Ataturk airport in 2015.

A US state department travel warning for Turkey, originally published in March and updated on Monday, urges US citizens to "exercise heightened vigilance and caution when visiting public access areas, especially those heavily frequented by tourists."