THREE people are missing feared dead, and 23 people have been rescued — some with serious injuries — after a US military aircraft went down off Rockhampton on Saturday afternoon.

The helicopter — an MV-22 Osprey tiltrotor helicopter, which can operate from aircraft carriers — was used as part of the giant Australian-US military exercise Talisman Sabre, which has just concluded.

It is understood the aircraft crashed at Shoalwater Bay near Rockhampton in the late afternoon.

Just in: Marine Corps announces search and rescue underway off Australia after MV-22 mishap. Small boats and warships searching — Barbara Starr (@barbarastarrcnn) August 5, 2017

Military sources said the accident happened as the aircraft attempted to land on the USS Ronald Reagan.

A search and rescue effort continues, with boats and warships searching for the missing personnel.

If confirmed, it would be the greatest loss of life in a military training accident in Australia since 18 servicemen died in a counterterrorism exercise when two helicopters collided near Townsville in 1996.

Four Bell-Boeing MV-22 Osprey aircraft were in Australia from US Marine Medium Tiltrotor Squadron 268, landing in Darwin at the end of April.

Sources told The Sunday Mail one seriously injured marine was being transported to Rockhampton Hospital.

It’s understood most of those rescued had serious injuries. There are no Australians involved.

US Marine aircraft crashes off Australia, search and rescue effort underway US Marine aircraft crashes off Australia, search and rescue effort underway

Prime Minister Malcolm Turnbull was travelling back from Western Australia but his office had been briefed on the incident.

Likewise US President Donald Trump, who has just begun a 17-day “working vacation”, at his New Jersey golf club, had been informed of the incident by his new chief of staff John Kelly, a White House official told reporters.

The strange-looking aircraft, resembling a cross between a helicopter and aeroplane, has capabilities including taking off vertically and travelling much faster than a helicopter.

In a statement, the US Military said: “The United States Marine Corps confirms there is an active search and rescue operation ongoing for service members involved in an MV-22 mishap off the east coast of Australia. Ship’s small boats and aircraft from the 31st Marine

Expeditionary Unit and Bonhomme Richard Expeditionary Strike Group are conducting the search and rescue operations. We will provide more details as they become available.’’

Our @QldPolice thoughts tonight r with all of our friends from the USS Bonhomme Richard. We pray 4 a miracle. @USConGenSydney — Ian Stewart (@CoPStewart) August 5, 2017

In a statement, federal Defence Minister Marise Payne has confirmed that no Australian Defence Force personnel were on board the aircraft.

“I have been advised of an incident involving a United States Marine Corps MV-22 Osprey helicopter off the coast of Shoalwater Bay today.

“The United States are leading the search and recovery effort.

“I have briefed Prime Minister Turnbull and spoken with Secretary Mattis this evening to offer Australia’s support in anyway that can be of assistance.”

“Our thoughts are with the crew and the families affected”.

A #31stMEU MV-22 flies over the horizon near @LHD6BHR. U.S. amphib training continues off the coast of Australia to be ready at all times. pic.twitter.com/HTu67mDk1O — AmphibForce7thFleet (@Amphib7FLT) August 4, 2017

The 31st Marine Expeditionary Unit shared photos of an Osprey helicopter conducting amphibious training from the USS Bonhomme Richard off the coast of Shoalwater Bay yesterday.

Since becoming operational with the US military in 2007, the MV-22 Osprey has had five serious crashes and several other accidents that have resulted in nine deaths.

The controversial aircraft was also involved in four crashes with 30 deaths during its testing phase between 1991 and 2000.

Osprey were used to escort Barack Obama’s presidential helicopter during the G20 in Brisbane in 2014.