A United States Marine Corps aircraft crashed on a north Australian island Sunday, killing three Marines and injuring 20 others taking part in a multi-nation training exercise, officials said.

Five of the injured were in a serious condition and were flown 50 miles (80km) to the mainland city of Darwin for hospital treatment after the Bell Boeing V-22 Osprey tiltrotor aircraft crashed on Melville Island at around 9.30m local time, a corps statement said.

“Recovery efforts are ongoing,” the statement said, adding that the cause of the crash is under investigation.

Northern Territory Chief Minister Natasha Fyles said: “We acknowledge that this is a terrible incident,” Ms Fyles said. “The Northern Territory government stands by to offer whatever assistance is required.”

Australian Prime Minister Anthony Albanese said only Americans were injured in the crash, which happened during Exercise Predators Run, which involves the militaries of the US, Australia, Indonesia, the Philippines and East Timor.

“The initial reports suggest that the incident involves just US defence force personnel,” he said.

“Our focus as a government and as the department of defence is very much on incident response and on making sure that every support and assistance is given at this difficult time,” he added.

Melville is part of the Tiwi Islands, which, along with Darwin, are the focus of the exercise that involves 2,500 troops.

Northern Territory Police Commissioner Michael Murphy said the Osprey that crashed was one of two that had flown from Darwin to Melville on Sunday.

Around 150 US Marines are currently based in Darwin and up to 2,500 rotate through the city every year.

The US military was also taking part in a multination military exercise in July when four Australian personnel were killed in an army MRH-90 Taipan helicopter crash off the north-east Australian coast.