A search was under way last night for three United States Marine Corps personnel who were reported missing after a "mishap" involving a military helicopter during a training exercise off the north-eastern coast of Australia.
The aircraft - an MV-22 Osprey tilt-rotor - crashed into the water during "regularly scheduled operations", the US Marine Corps said.
The accident occurred off the coast of Shoalwater Bay in the state of Queensland, a training area that was used for the recently completed biennial Talisman Sabre joint training exercise between Australian and US military forces.
The US Marine Corps said last night that 23 of the 26 troops aboard the aircraft had been rescued.
"The aircraft involved in the mishap had launched from the USS Bonhomme Richard and was conducting regularly scheduled operations when the aircraft entered the water," it said in a statement. "The ship's small boats and aircraft immediately responded in the search and rescue efforts."
According to Queensland's Courier Mail, most of those wounded had serious injuries.
A spokesman for Queensland Ambulance, Mr Michael Augustus, said one person had been taken to hospital in the city of Rockhampton. Most of the injured were reportedly being treated on a warship.
Australian Defence Minister Marise Payne said she had spoken to US Defence Secretary James Mattis to offer support. No Australians were aboard, she added.
"The United States is leading the search and recovery effort," she said in a statement. "I have briefed Prime Minister (Malcolm) Turnbull and spoken with Secretary Mattis this evening to offer Australia's support in any way that can be of assistance. Our thoughts are with the crew and families affected."
The Osprey, a mix between a helicopter and an airplane, can travel much faster than regular helicopters. But it has been involved in several serious crashes, which have reportedly led to over 20 deaths.
Most recently, three soldiers were injured after an Osprey made a "hard landing" during a raid in Yemen in January.
Last December, the US grounded its fleet of the aircraft in Japan after a crash landing - also described as a "mishap" - off the coast of Okinawa.
The Talisman Sabre exercise, which involved 33,000 troops from Australia and the US, its ally, concluded on July 25.