Filipino and Vietnamese troops played football and tug-of-war on a disputed South China Sea island on Wednesday, officials said, closing ranks as their rival China ramps up construction of artificial islands.

The games took place on Philippine-held Northeast Cay, just 2.7 kilometres (1.7 miles) from Southwest Cay which is controlled by Vietnam, where a similar contest was held last year.

"It was a navy-to-navy confidence-building engagement," Vice Admiral Alexander Lopez, the Philippine military commander in the Spratly island region, told AFP.

Troops also played volleyball and held a sack race, navy spokesman Colonel Edgard Arevalo said, adding that it was not immediately known which side won the games on the remote island.

"Interpersonal interactions like this intend to bring out camaraderie and understanding," Arevalo said in a statement to AFP.

"It intends to enhance cordial relations while engaging opponent teams through sports events."

Northeast Cay, a 12-hectare (30-acre) leaf-shaped sandy island, is claimed by the Philippines as part of its Kalayaan (Freedom) municipality.

It is located roughly 70 kilometres from Subi reef, the nearest Chinese-controlled feature.

The sporting content and show of solidarity was staged as China ramps up construction on disputed reefs, in an ambitious program that has raised fears of militarisation of the strategically important sea.

Last week, the Chinese military ordered a US Navy P-8 Poseidon surveillance plane to leave airspace above the disputed Spratly islands.

It has issued similar warnings to at least seven Filipino patrol planes that flew between Philippine-held Thitu island and Chinese-held Subi reef since April, according to the Philippine navy.

Philippine President Benigno Aquino said on Monday that his country would defy China's warnings and keep flying over the disputed areas.

China claims almost the entire South China Sea, even waters near the coasts of its neighbours.

The Philippines, Vietnam, Malaysia, Taiwan and Brunei also claim parts of the sea, which hosts major sea lanes and is believed to hold vast mineral deposits.

Last year, China moved a deep-water oil rig into South China Sea waters claimed by Vietnam, sparking a months-long high seas standoff.

The Chinese later removed the rig after a series of violent protests in Vietnam.

The Philippines, meanwhile, has asked a United Nations-backed arbitration body to rule on the legality of China's claims and expects a ruling by early next year.

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April