China on Monday expressed displeasure after Vietnamese and Filipino troops played sports together on a contested island, with the foreign ministry denouncing the activity as "a farce".

The retort from Beijing came one day after Vietnam hosted Filipino troops on an island it controls in the disputed Spratlys archipelago in the South China Sea that the Philippines' navy said was designed to "foster camaraderie".

Tensions between China and both countries have risen in recent months over contested territory in the region, with a dispute between Hanoi and Beijing triggering violent anti-Chinese riots in Vietnam last month.

Asked about the joint sports activity, Chinese foreign ministry spokeswoman Hua Chunying said Monday at a regular briefing: "Don't you think that these small tricks conducted by the Philippines and Vietnam are nothing but a farce?"

She also urged Hanoi and Manila to "refrain from taking any actions that may complicate or magnify the dispute" and said that China "exercises indisputable sovereignty over the Nansha Islands and adjacent waters", referring to the Spratlys by their Chinese name.

The first-ever joint games between the Philippine and Vietnamese navies saw them play football and volleyball and were designed to "foster camaraderie" among the troops, Philippine Navy spokesman Lieutenant Commander Gregory Fabic said.

"This also serves as a model of cooperation for the other navies to emulate," Fabic added, without mentioning China by name.

The Spratlys are a disputed group of reefs, islands and atolls coveted by the Philippines, Vietnam, China, Malaysia, Brunei and Taiwan.

The region is believed to sit atop oil and other mineral deposits and all of the claimants, save for Brunei, have troops in the islands.

Tensions between China and Vietnam have escalated sharply in recent weeks following Beijing's dispatch of an oil rig to waters surrounding another contested island group, the Paracels.

Last week, Vietnam released dramatic footage showing a large Chinese ship chasing and ramming one of its fishing boats, which then sank near the rig.

Beijing responded Monday by issuing a lengthy defence of its use of the rig on both the foreign ministry website and via the official Xinhua news agency.

"We find it necessary to tell the international community what really happened so as to restore the truth," Hua said when asked about the document.

China is asking Vietnam to "bring those lawbreakers to account and make full compensations to China," she added.

The Philippines -- which has filed a plea to the United Nations challenging Beijing's claims to about 70 percent of the South China Sea -- said Saturday it was investigating reports that China was reclaiming land in the Spratlys area.

Hua said she was unable to verify or comment on the reports but maintained that "what kinds of activities China is going to conduct in the Nansha Islands is within China's jurisdiction".