SYDNEY (Reuters) - A "tragic" incident involving a U.S. military aircraft occurred in northern Australia during military exercises on Sunday, Prime Minister Anthony Albanese said, adding that his government was focussed on providing support.

Sky News Australia reported a v-22 Osprey helicopter with about 20 U.S. Marines on board had crashed off the coast of Darwin. The Australian Broadcasting Corporation (ABC) said one person was in critical condition, two were stable and there were no reports of fatalities.

Albanese, speaking at a previously scheduled press conference, declined to provide details about the crash or rescue efforts, which he said took place on Melville Island north of Darwin during Exercise Predator’s Run 2023.

"Our focus as a government and as a 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 said.

Australian personnel were not involved, Albanese said.

Northern Territory Police were responding to reports of an aircraft crash on Melville Island, the fire and emergency services said in an emailed statement.

The U.S. Defense Department was aware of media reports about the crash "but we do not have anything we can provide at this time", a duty officer said in an emailed statement.

The U.S. and Australia, a key ally in the Pacific, have been stepping up military cooperation in recent years in the face of an increasingly assertive China.

Four Australian soldiers were killed last month during large bilateral exercises when their helicopter crashed into the ocean off the coast of Queensland.

(Reporting by Sam McKeith in Sydney and Shivani Tanna in Bengaluru; Editing by William Mallard)