Manila: Vietnamese and Philippine troops played soccer and sang karaoke on a South China Sea island on Wednesday in a sign of the growing security ties between the two Southeast Asian nations most at odds with Beijing over the contested waterway.

Cooperation has blossomed between Hanoi and Manila since they shelved decades of enmity over their competing claims in the Spratly archipelago to try to counter China, whose creation of artificial islands in the region will allow it to project power deep into the maritime heart of Southeast Asia.

Senior Philippine naval officials said soccer and volleyball games were being played on the Philippine-held island of Northeast Cay. A Vietnamese navy ship had earlier brought about 60 Vietnamese sailors to the island, where 100 Filipino troops were present, they said.

“We will have a good time together. These activities are helping raise the comfort level of troops in the disputed area and will strengthen relations between our two navies,” said a senior Philippine naval official who declined to be identified.

Chinese Foreign Ministry spokeswoman Hua Chunying said she was not aware of the activities but that China’s consistent position was that “we are not going to disturb others”.

“But as for China’s sovereignty and territorial integrity, our will and ability to defend it is there,” Hua said at a regular news briefing.

Tensions have risen in the Spratlys in recent months as China has sought to assert its claim to the potentially energy-rich waters, warning Philippine and U.S. military aircraft away from the reefs it is turning into islands.

Both Beijing and Washington have accused each other of stoking instability.

China claims most of the South China Sea, through which $5 trillion (Dh18.36 trillion) in ship-borne trade passes every year.

The Philippines, Vietnam, Malaysia, Taiwan and Brunei also have overlapping claims. Fortifications belonging to all claimants except Brunei are dotted across the Spratlys.

Last year, Philippine troops visited the Vietnamese-held island of Southwest Cay, just a few kilometres from Northeast Cay, for similar games.

Since then, Vietnamese warships have visited Manila. A naval hotline has also been established, which has helped in the return of fishermen who get into trouble in the open sea.

Philippine military officials also recently said both sides had informally discussed conducting joint naval patrols in the South China Sea.

A Vietnamese military official said the Philippines had raised the idea some time ago but that nothing was fixed.

Diplomats and experts describe the nascent partnership as part of a web of evolving informal alliances across Asia that are being driven by fear of China.

“A Manila-Hanoi axis places a hurdle in China’s ambitions to control most of the South China Sea,” said Patrick Cronin, an expert on the region at the Center for a New American Security in Washington.

“This may not lead to immediate changes in the regional balance of power ... but it will shine a spotlight on how China’s assertive unilateralism threatens to undermine stability and prosperity.” Coincidentally, the Philippines occupied Southwest Cay until early 1975, when troops from then South Vietnam seized it after Philippine forces sailed to nearby Northeast Cay for a party.

The South Vietnamese were soon displaced by the communist forces of a victorious Hanoi.

Manila and Hanoi still claim both islands.