A United Airlines flight took a u-turn in mid-air Monday, after a rowdy passenger stormed the cockpit screaming "jihad, jihad!". 

The incident comes as the United States and its allies have been stepping up security against possible attacks by terror group ISIS.

A government official said there had been no established link between the man and known terror groups, but his act was considered alarming. Officials have not confirmed the man's mental state at the time of his unruly behavior.

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United Airlines Flight 1074 took off from Washington Dulles International Airport and was flying to Denver International Airport when the incident happened.

The Boeing 737 plane was carrying 33 passengers and six crew members.  United Airlines spokesman Luke Punzenberger said the passenger had failed to comply with crew's in-flight instructions.

"He ran forward toward the cockpit, and he is being restrained by passengers," one of the pilots said. "Cockpit is secure, and we would like to return to the airport and have the authorities meet him."

The pilots immediately reported to air traffic controllers when the passenger turned violent.  The man was caught on video, with bruises on his face, after being held down by other passengers.

"Don't move," one passenger was heard talking.  "You're OK. We're going to get you off this plane, buddy."

The Metropolitan Washington Airports Authority said the plane landed back at Dulles around 10:40 p.m. ET.

The unruly passenger was immediately taken out of the plane and was transported to a local hospital for further evaluation.

There were no reports of injuries nor weapons seized.  All passengers will be flown to Denver on Tuesday. 

TagsUnited Airlines, ISIS, jihad, terror scare