TWO British Royal Navy helicopters collided in the early hours of Saturday morning over the Persian Gulf, killing all seven on board.

The two Sea King helicopters were not struck by enemy fire, said Group Capt. Al Lockwood, a spokesman for British forces in the Gulf.

"All those on the helicopters have perished," Lockwood said. "It's a great tragedy."

The helicopters crashed about 4:30 a.m., just after taking off from a ship in the gulf, officials said. The cause was under investigation.

"We do have very careful plans and procedures to ensure we have separation of all the aircraft being used," Group Capt. Lockwood said. "Sadly, last night something was not quite right and we are looking to find out what that was as quickly as possible."

Pentagon spokesman Maj. Ben Owens said a U.S. Navy officer was among the seven on board who died, the accident is the second involving coalition helicopters since the campaign began.