Australia and the Philippines have begun joint sea and air patrols in the South China Sea as Pacific nations warily eye an increasingly assertive China.
The three-day exercises follow discussions earlier this year on joint patrols to underscore what the countries say is their commitment to closer cooperation and a rules-based order in the region.
It also comes days after Manila took similar steps with the United States, concluding patrols that started in waters near Taiwan.
Defence Minister Richard Marles said the inaugural patrols represent the practical implementation of the strategic partnership signed between the two nations in September.
"Australia and the Philippines are firmly committed to a peaceful, secure and prosperous region, where sovereignty and agreed rules and norms are respected," he said in a joint statement with the Philippines' National Defence Secretary Gilberto C Teodoro Jr on Saturday.
"The first maritime cooperative activity between the Australian Defence Force and Armed Forces of the Philippines demonstrates this important commitment."
The Philippines department of defence spokesperson Arsenio Andolong said the patrols will be carried out in the West Philippine Sea, Manila's term for waters in the South China Sea that fall within its exclusive economic zone.
The Philippine military said two of its navy vessels and five surveillance aircraft would participate.
Australia said it would send the frigate HMAS Toowoomba and P8-A maritime surveillance aircraft.
Philippines President Ferdinand Marcos Jr hailed the exercises as maintaining a rules-based international order.
"This inaugural Maritime Cooperative Activity and those that may follow are a practical manifestation of the growing and deepening strategic and defense partnership between our countries," he said on the social media platform X, formerly known as Twitter.
China claims almost the entire South China Sea, a conduit for more than $3 trillion of annual ship-borne commerce, including parts claimed by the Philippines, Vietnam, Indonesia, Malaysia and Brunei.
The Permanent Court of Arbitration in 2016 said China's claims had no legal basis.
The Philippines is ramping up efforts to counter what it describes as China's "aggressive activities" in the South China Sea, which has also become a flashpoint for Chinese and US tensions around naval operations.
China has accused the Philippines of enlisting "foreign forces" to patrol the South China Sea. Manila insists the maritime activities are within its rights.
Earlier this year, Prime Minister Anthony Albanese vowed to take Australia's relationship with the Philippines to the next level, after the two nations signed closer defence and security ties.
Australian Associated Press