All seven crew members were presumed dead after two Royal Navy helicopters collided over international waters in the Gulf on Saturday, British military officials said.
A search and rescue operation was underway, but no crew members had yet been found, Britain's Ministry of Defense said, adding it believed there were no survivors.
Earlier, two Royal Navy helicopters collided over international waters in the Gulf and seven crew members were missing, officials said.
Group Capt. Al Lockwood, a spokesman for British forces in the Gulf, said the mid-air collision involved Sea King Airborne Early Warning helicopters.
Speaking at UK Central Command in Qatar, Lockwood said a search and rescue operation was underway to find the missing crew members.
"We are doing everything we can to ascertain what caused the accident," he told Sky News.
A spokesman at UK Central Command in Qatar told Britain's Press Association news agency the crew members were feared dead.
"There are believed to be no survivors," he said, on condition of anonymity.
The accident happened at around 4:30 a.m. local time (0700 IST). Lockwood said the collision was not the result of enemy fire.
"The most important thing at this moment is with notifying next of kin of the casualties," he said. "Circumstances are still unclear. An investigation is under way and obviously it will take some time to ascertain what happened."
The accident is the second involving coalition helicopters since the US-led campaign began.
The accident is the second involving coalition helicopters since the US-led campaign began.
Eight British Royal Marines and four American Marines died when a CH-46 Sea Knight helicopter crashed before dawn in Kuwait yesterday.
Lt. Col. Ben Curry, a British Royal Marines spokesman, said that crash occurred as troops were being deployed to seize oil fields on the Al Faw peninsula in southern Iraq.