British police arrested three passengers on a Dubai-bound Emirates airliner on the ground at London's Heathrow airport , last night, after verbal threats were made before the take off, police said.

Sky News, quoting police sources, reported that three young Englishmen had been taken off the plane and said police searches had not found any threat to the flight, indicating that the incident could have been an ill-judged prank.

An airport spokesman said other flights at Britain's biggest airport were unaffected. Witnesses told Sky that armed police with sniffer dogs had boarded flight EK004, which had been due to take off at 2000 GMT, and removed the passengers.

"It looks like there was some sort of verbal threat made," a police spokesman said. "They are currently in custody. The airport remains open."

Airports around the world have been on high alert since a failed bombing attempt on a Detroit-bound plane last month. Britain announced tighter security measures this week, with plans to use full body scanners at Heathrow within three weeks.

"There was no shouting or screaming ... They took them away quickly and brought on some dogs to have a sniff around," Cameron McLean, a passenger on the grounded Boeing 777, told Sky News. "I think we are all going to have to get off and then reboard. People are just bored and want to get on with our flight."