China's military issued "robust" challenges to three Australian warships as they travelled through the South China Sea to Vietnam earlier this month.
Defence sources told the ABC the confrontations between HMAS Anzac, HMAS Toowoomba and HMAS Success and the People's Liberation Army occurred ahead of the Australian vessels' arrival for a three-day goodwill visit in Ho Chi Minh City.
One official, speaking on the condition of anonymity, told the ABC exchanges with the PLA Navy were polite, but "robust".
Prime Minister Malcolm Turnbull would not reveal what happened in the exchange with the Chinese military when questioned about it on the sidelines of the CHOGM meeting in London on Thursday local time.
"All I can say to you is Australia asserts and practices its right of freedom of navigation throughout the world's oceans, including of course the South China Sea," Mr Turnbull said.
"As is our perfect right in accordance with international law."
The Defence Department confirmed the three vessels recently travelled through the South China Sea, but refused to provide details of the interactions between Australia's warships and Chinese military, the ABC reported on Friday.
The aircraft carrier Theodore Roosevelt (CVN-71) is sailing through the disputed South China Sea in the latest display of America's military might. Source: AAP
"The Australian Defence Force has maintained a robust program of international engagement with countries in and around the South China Sea for decades," the department said in a statement.
"This includes bilateral and multilateral military exercises, port visits, maritime surveillance operations and ship transits.
Chinese President Xi Jinping in the South China Sea. China has announced live-fire military exercises in the Taiwan Strait. Source: AAP
"As they have done for many decades, Australian vessels and aircraft will continue to exercise rights under international law to freedom of navigation and overflight, including in the South China Sea."
