The submarine Kuroshio on Thursday joined three Japanese warships in waters just southwest of the China-controlled Scarborough Shoal, the Asahi Shimbun said.

China claims most of the resource-rich South China Sea, through which $5 trillion in shipping trade passes annually, despite competing claims from Brunei, Malaysia, the Philippines, Taiwan and Vietnam.

Tensions have been high over the Scarborough Shoal since Beijing seized it from Manila in 2012.

The newspaper said the submarine exercises were Tokyo's first in the South China Sea.

The Maritime Self-Defence Force carried out a "practical" anti-submarine drill, including an exercise to spot enemy submarines with sonar devices, the Asahi said, quoting government sources.

The sources described it as a legitimate naval exercise in neutral waters, with rights of access secured under international law.

Immediate confirmation of the Asahi Shimbun report was not available.

Chinese foreign ministry spokesman Geng Shuang declined to confirm the drill, but said that "the situation in the South China Sea is improving".

Japan "should act cautiously and avoid doing anything which would harm regional peace and stability", he told a regular press briefing.

Following the drill, the Japanese submarine plans to make a port call on Monday at Cam Ranh in central Vietnam, to promote defence cooperation with Hanoi, the Asahi said.

It will be the first call by a submarine at the strategically important port since the Second World War, it added.

China has engaged in years of land-reclamation efforts on reefs it controls in the South China Sea and has built both civilian and military facilities on them.

Earlier this month Beijing lashed out at Britain for sending a warship close to the disputed islands -- one of a series of "freedom of navigation" operations carried out in recent times by the US and its allies.