Units from the countries of Asean began their first ever joint military drills in Indonesia's South Natuna Sea amid rising geopolitical tensions between major powers and protests against China's activities in the South China Sea.
The five-day non-combat operation is aimed at developing military skills, including maritime security and patrols, and the distribution of humanitarian assistance and disaster relief, the Indonesian military said in a statement.
All 10 members of Asean will join the exercise, including prospective member East Timor.
"This is not a combat operation because Asean is more focused on economics. The training is more about social activities," Yudo Margono, Indonesia's military chief, told reporters after the opening ceremony on the Indonesian island of Batam on Tuesday.
The drills, which were relocated because of the sensitivities of the initial location, are being held amid diplomatic protests over China's release last month of its "10-dash line" map, which expands its claims to cover about 90% of the South China Sea. More than US$3 trillion (RM14.09 trillion) in trade passes through the strategic maritime area each year.
The exercises were originally set to take place in the southernmost waters of the South China Sea, which are also claimed by Beijing.
The Philippines, Malaysia, Taiwan, and Vietnam rejected China's map, describing it as baseless. Malaysia also filed a related diplomatic protest.
During the 43rd Asean Summit in Jakarta earlier this month, Philippine President Ferdinand Marcos said his country did not seek conflict in the South China Sea, but had a duty to "meet any challenge to our sovereignty".
Earlier this month, the Philippines condemned China's coast guard for harassing boats resupplying Philippine troops on an uninhabited atoll in the disputed Spratley Islands in the South China Sea.
Asean has been discussing a code of conduct on the South China Sea for more than 20 years with little progress to date.
The Philippines and some other Asean members have grown frustrated over a lack of progress on the code.
Asked about rising geopolitical tensions, Indonesia's Margono reiterated that the drills this week were non-combat in nature.