Southeast Asian forces gather for joint military drills

It will culminate in a "combined amphibious assault exercise" in Indonesian waters between Surabaya and Bali in November.

The drills form part of the broader regional exercise Indo-Pacific Endeavour that will involve deployments in the South China Sea, parts of which Beijing contests as its own, resulting in repeated clashes with Philippines vessels.

Actions by the Chinese military against Australian aircraft and navy personnel conducting freedom of navigation exercises in the area have been called dangerous and unprofessional by Canberra.

A top international court has ruled China's territorial claim to the sea had no legal basis, which Beijing rejects.

Endeavour Commander Michael Harris said he expected Chinese navy ships in the contested waters to abide by international law after provocations from Beijing.

"We engage with countries around the rim of the South China Sea," he told a small media briefing ahead of the exercise's commencement.

"It's a local environment for the PLA (People's Liberation Army), we have interactions that are respectful of sovereignty and international law and I'd expect if we have any interactions that will continue that way."

Around 3500 Australian defence personnel and up to five navy ships are expected to take part in the Indo-Pacific Endeavour exercise alongside Southeast Asian counterparts.

It includes personnel from Australia, Bangladesh, Brunei, Cambodia, India, Indonesia, Laos, Malaysia, Maldives, the Philippines, Singapore, Sri Lanka, Thailand, East Timor and Vietnam.

Port visits, humanitarian assistance and disaster relief efforts, military training and cultural activities form part of the five-month exercise.

Australia joined Canada, the Philippines and United States warships sailing through the South China Sea as part of a separate freedom of navigation drill on August 7 and 8.

Indo-Pacific Endeavour began in 2017 as an annual defence exercise co-ordinated by the Australian Defence Force.