MANILA, Philippines — The Chinese Navy challenged Australian warships passing through the disputed South China Sea earlier this month, according to a report.

Australian broadcast network ABC News reported that HMAS Anzac, HMAS Toowoomba and HMAS Success were en route to Vietnam and China's PLA Navy was conducting naval exercises in the South China Sea when the confrontation happened.

HMAS Anzac and HMAS Success passed through the contested waters after leaving Subic Bay in the Philippines.

An Australian Defense official told ABC News that the exchanges between the Australian warships and the Chinese navy were polite but "robust."

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The Australian Department of Defense, however, refused to comment on the issue but confirmed that the three warships went through the disputed waters.

The Defense department told ABC News that the Australian Defense Force maintains a robust program of international engagement with countries in and around the South China Sea.

"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," the Australian Defense Department said in a statement.

Australia has increased its naval presence in the South China Sea amid China's militarization activities in the region.

Earlier this year, Australian Defense Minister Marise Payne confirmed that Canberra has stepped up its naval presence in the disputed waterway in the last 18 months.

Beijing had reportedly implemented a "diplomatic deep freeze" over Canberra following Australian Prime Minister Malcolm Turnbull's foreign interference laws and naval challenges in the South China Sea.

Australia, an ally of the United States, has been expressing concern over China's expansive claims in the South China Sea.