(CNN) Prime Minister Malcolm Turnbull asserted the right of the Australian navy to travel the South China Sea, after local media reported three Australian warships were challenged by the Chinese navy earlier this month.

As the three vessels traversed the hotly contested waters on their way to Vietnam, they were confronted by the People's Liberation Army (PLA) navy, the Australian Broadcasting Corporation reported on Friday.

The ABC said that one Australian defense official, speaking on condition of anonymity, "insists the exchanges with the Chinese were polite, but 'robust'."

Prime Minister Malcolm Turnbull, in London for a meeting of the heads of Commonwealth nations, refused to confirm or deny the report.

"All I can say to you is that Australia asserts and practices its right to freedom of navigation throughout the world's ocean, including the South China Sea," he told reporters.