China's military issued "robust" challenges to three Australian warships as they travelled through the South China Sea to Vietnam this month.
Defence sources say the confrontations between HMAS Anzac, HMAS Toowoomba and HMAS Success and the People's Liberation Army occurred before 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".
Defence Industry Minister Chris Pyne said Chinese authorities "asked questions" of the vessels travelling through the sea but said he would not describe the exchange as a confrontation.
"From what I understand, in the normal course of events, questions are asked, sometimes more robustly than other times," Mr Pyne told reporters in Adelaide on Friday.
"That doesn't change our views about being able to navigate the South China Sea.
"We will continue to so along with the United States. We do it very, very regularly with all kinds of commercial vessels but also with our navy platforms."
Prime Minister Malcolm Turnbull would not reveal exactly what happened in the exchange with the Chinese military when questioned 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 the Chinese military, the ABC reported on Friday.
"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.
"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."
