SYDNEY: Australia's defence minister said on Monday there was little hope of finding alive the four aircrew aboard a military helicopter that crashed into the sea off Queensland state.

The MRH-90 helicopter was taking part in Talisman Sabre military exercises between the United States and Australia when it came down in waters close to Hamilton Island, about 890 km (550 miles) north of Brisbane, late on Friday.

"There was a catastrophic incident and with every passing hour, it is now clear that any hope of finding (the soldiers) has been lost," Defence Minister Richard Marles said during a media briefing.

Marles said the rescue operation involving hundreds of military personnel had found "significant wreckage" from the helicopter. The MRH-90 fleet would be grounded until the investigation into the crash was finished, he said.

Defence Force Chief Angus Campbell said recovering the bodies of the four aircrew would not be easy due to strong currents but the operation was continuing.

"We're going to do everything possible to bring our mates home to their families," he said.

Australian Defence on Sunday named the missing soldiers as Captain Daniel Lyon, Lieutenant Maxwell Nugent, Warrant Officer Class Two Joseph Laycock and Corporal Alexander Naggs.