Witnesses said a blazing Cherokee jeep containing two Asian-looking men crashed through the doors of the main terminal building.

A man with his clothes on fire got out of the vehicle and was restrained by passengers and police while others put out the flames with a fire extinguisher. Two men were later arrested.

The airport was closed and passengers were cleared from the terminal building amid fears that it was a terrorist attack.

The incident came as police in London continued to search for terrorists who planted two car bombs which failed to detonate in the heart of the capital.

A spokesman for the airport's operators, the British Airports Authority, said emergency services were at the scene.

He said: "A car is on fire at the entrance to the terminal and there is considerable smoke damage to the terminal. The terminal has been evacuated as a result of this and all flights have now been suspended. This is the start of the busy summer holiday period, although Saturdays are less busy than week days.

"But this will cause disruption and our advice to passengers is to check with their airline to establish if their flight will be operating."

Another eyewitness, taxi driver Ian Crosby, said he was in no doubt that it was a terrorist attack.

"It looks to me like these people were intent on doing some serious damage," he told the BBC. "There was smoke coming from inside of the back seats," he said. "Immediately I realised this was a terrorist attack. Somebody had planned this. This was no accident."