The Philippines joined Canada, Australia, and the US for naval drills amid territorial threats from China in the South China Sea.

The allied nations participated in a Multilateral Maritime Cooperative Activity - the 10th since April 2024 - held off Zambales province from September 2 to 3.

The Armed Forces of the Philippines (AFP) said in a statement: 'Key serials included a Photo Exercise (PhotoEx) that captured the unity of participating navies, a Vertical Replenishment (VERTREP) to test at-sea logistics and resupply operations, and a Personnel Exchange conducted via RHIB that enabled Australian and Philippine sailors to share best practices onboard.

'The activity also featured a Coordinated Anti-Submarine Warfare Exercise (CASEX C2 Reverse), which enhanced detection and tracking capabilities, and concluded with a Passing Exercise (PASSEX), underscoring the seamless coordination and interoperability of all participating forces.'

Two Chinese warships were reportedly seen observing the exercises at a distance.

Rear Admiral Roy Vincent Trinidad, Philippine Navy spokesman for the West Philippine Sea, said: 'These ships were monitored during the conduct of the 10th MMCA involving the US Navy, the Royal Canadian Navy, the Royal Australian Navy and the Philippine Navy.

'They were observed following the international task group and were not conducting any surface serials or synchronized movement that would generally indicate a joint patrol contrary to publications by the Southern Theater Command.'

The United States and the Philippines are treaty allies under the 1951 Mutual Defense Treaty, pledging mutual support in case of an armed attack in the Pacific.

The significance of the alliance has been underscored amid escalating territorial tensions between the Philippines and neighbouring China over parts of the South China Sea.

Expansionist China currently lays claim over almost the entire South China Sea, one of the world's busiest sea lanes. But a United Nations-backed tribunal in 2016 deemed its claims groundless.

The Communist rogue state - accused of genocide for its crimes against the Uyghur population - has been steadily increasing its influence in recent years through investment in developing countries.