Australian Defence Minister, Richard Marles, on Monday said Authorities have lost hope of finding survivors after a military helicopter plunged into the sea during war games over the weekend.

Marles noted that rescuers initially hoped they would find the four crew members alive, but it was dashed after the discovery of "significant wreckage" from the aircraft.

Access24 reports that the chopper had been taking part in the large-scale Talisman Sabre exercise, which brings together 30,000 military personnel from Australia, the United States, and several other nations.

It plunged into the water near the Whitsunday Islands while taking part in a nighttime operation.

"There was a catastrophic impact, and that forms part of why we are now transferring this from an activity of search and rescue, to one of recovery," Marles told reporters.

Militaries from at least three nations had joined police in looking for the crew of the MRH-90 Taipan, which went down late Friday night in subtropical waters off the northeast coast of Australia.

"The loss of these four men is as significant and meaningful as the loss of anyone who has worn our nation's uniform," Marles said, adding he was "deeply sorry" for their families.

"Amidst the inadequacy of these words, I want them to know they stand in the warm embrace of the entire nation."