A man was arrested by Serbian authorities after he allegedly attempted to open an emergency exit on a Lufthansa flight REUTERS/Louis Nastro

A man has been arrested after he allegedly threatened to open one of the doors on a plane during a Lufthansa flight. The man was restrained as he fumbled with the controls of an emergency exit door during the flight from Frankfurt to Belgrade, the German airline said.

Passengers told Serbia's public broadcaster RTS that the suspect got up mid-flight, banged on the cockpit door and demanded to be allowed in. He reportedly threatened to bring down the plane and shouted that he wished to join Allah along with all the passengers.

"A passenger got up and tried to do something at the door, but was stopped by crew members and other passengers," said Lufthansa spokesman Andreas Bartels. "The passenger was then restrained for the remainder of the flight in his seat and handed over to the authorities in Belgrade."

Mr Bartles stressed that the door the man was trying to open was not to the cockpit. "It was a normal door, which of course cannot be opened in-flight... it was not the cockpit door," he said. "The safety of the flight was not jeopardised and the flight landed safely in Belgrade."

The incident happened as the plane was flying over Austria. Cabin crew and passengers overpowered the Jordanian suspect, who had an American passport. Serbian authorities arrested him when the plane reached Belgrade, Sky News reports.

The crew and passengers who subdued him - which included members of a Serbian handball team - kept the man restrained for the rest of the flight.

The suspect is being held in pre-trial detention on the grounds of endangering public safety.