Three Royal Navy personnel have died in a helicopter crash during a training exercise in Devon.
Emergency services were called to Sourton Down, near Okehampton, at about 03:45 BST after a Merlin Mk4 crashed.
A Royal Navy spokesperson said it was "with deep sadness that we can confirm three members of the Royal Navy have died during a helicopter training exercise".
They added: "The families of the service personnel have been informed and have requested a period of grace before further details are released. Our thoughts and sympathies are with their families and friends at this sad time."
Head of the Navy, General Sir Gwyn Jenkins said: "I know this will come as a huge shock to all in our Naval community, and my deepest condolences go out to the families, friends and loved ones impacted by this tragedy."
He confirmed that the helicopter was a Merlin Mk4, which are known to be based at RNAS Yeovilton in Somerset.
He also thanked Devon and Cornwall Police and the search and rescue teams who responded to the crash.
Defence Secretary John Healey said he was "devastated by the loss of three service personnel".
The Merlin helicopter entered service with the Royal Navy in 1999. There are two versions in use, the Mk2 and Mk4.
Merlin Mk2 helicopters are based at RNAS Culdrose in Cornwall with the Merlin Helicopter Force, which operates 30 Mk2s. This version is primarily an anti-submarine helicopter.
Merlin Mk4 helicopters are based at RNAS Yeovilton in Somerset with the Commando Helicopter Force, which operates 25 Merlin Mk4 helicopters for the Royal Marines.
Military helicopters often train in the area around north Dartmoor, which lies between the air bases at Yeovilton and Culdrose.
The devastating wreckage of the helicopter is visible in the field.
Witnesses at the scene said they heard noises that sounded like "troubled mechanics" as a helicopter flew over.
One described it as "sounding not right" as it flew over his house and said "it almost took the roof off" his home.
The scene is also close to Okehampton battle camp, a military facility on the edge of Dartmoor which has been used for training Merlin helicopter crews from the Commando Helicopter Force.
Prime Minister Sir Keir Starmer told the Commons during Prime Minister's Questions: "This will be a deeply worrying time for the families and more information will be set out as soon as possible."
Devon and Cornwall Police Chief Constable James Vaughan said the emergency services, navy and Civil Aviation Authority attended the scene.
"We continue to investigate the circumstances surrounding that crash," Vaughan added.
Devon and Somerset Fire Service said seven engines from six stationshad been dispatched.
"Several specialist resources were also deployed including an Environmental Protection Unit, Welfare Unit, Command Unit and an Urban Search and Rescue team," a fire service spokesperson said.
"One appliance remains at the scene."
The A386 between the A30 at Sourton Down and the A3079 Fowley Cross in Okehampton was closed at about 04:30.
The A386 reopened at about 13:30, but National Highways said the eastbound exit slip road of the A30 remained closed.
Staff at Sourton Cross Service Station, which is located near the scene, said the services were currently inaccessible.
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