Three US Marines were killed on Sunday when their Osprey aircraft crashed on a remote Australian island during a training exercise.
US officials said another five crew members were injured and had been flown from the isolated crash site to Royal Darwin Hospital in a “serious condition”.
The US Marine Rotational Force in Darwin said there were a total of 23 personnel on board at the time of the crash.
Australia’s military said only Americans were involved.
Rescue efforts were complicated by the remote location of the crash, on the sparsely populated Melville Island. It is about 37 miles north of the nearest city, Darwin.
The aircraft was taking part in a training exercise called “Predators Run”, a series of drills involving thousands of soldiers from the US and Australia, as well as other militaries, including from Indonesia and the Philippines.
Ospreys are described by the US Air Force as combining the features of both helicopters and turboprop planes.
The hybrid aircraft have two swivelling engines positioned on fixed wingtips that allow them to land and take off vertically. They also travel much faster than a conventional helicopter.
‘Tragic and regrettable’
Anthony Albanese, the Australian prime minister, and Richard Marles, the country’s defence minister, extended their “deepest condolences” to the US military following the crash.
“This incident is a reminder of the significance of the service undertaken by our personnel and those of our partner nations,” they said in a joint statement.
Mr Albanese also described the crash as “tragic” and “regrettable”, and stressed that authorities were still trying to piece together what had happened.
“This is a difficult incident, we are responding fully, and our priority is on providing every assistance possible,” he said.
Local authorities said Royal Darwin Hospital had activated its highest emergency alert as intensive care staff braced for the arrival of injured crew.
Northern Australia has become an important staging ground for the US military in recent years, as Washington and Canberra work together to counter China’s growing clout in the Asia-Pacific region.
Investigators will now begin piecing together what led to the crash on Melville Island, which is known for coral reefs, pristine beaches, and the vibrant culture of its Indigenous-Australian inhabitants.
The US Army earlier this year temporarily grounded all pilots who were not involved in critical missions, forcing them to complete further training, after a series of safety incidents.