TOKYO • Japan's top government spokesman yesterday said it was unacceptable that Chinese coastguard vessels had approached Japanese trawlers near disputed islands for two straight days this week, in a sign of rising tension between the Asian neighbours.

Chief Cabinet Secretary Katsunobu Kato told a news conference that Japan had protested against the incidents which took place in what the country sees as its territorial waters near uninhabited East China Sea islands.

Ships from Asia's two largest economies have chased one another around the chain, known as Senkaku in Japan and Diaoyu in China, since the Japanese government bought three of the islands from a private landlord in 2012.

Focus on the islands was intensified after US President Joe Biden took office and assured Prime Minister Yoshihide Suga that Washington would stand by its security treaty commitment to defend the islands controlled by its ally Japan.

The conversation came as the Biden team staked out early opposition to Chinese territorial claims in a series of calls to Asian allies last month.

Beijing, which has in turn protested against what it says are unlawful moves by Japanese vessels near the islands, has sometimes appeared to use the escalation of its coastguard activities in the waters as a means of challenging Japanese actions.

China last month passed a law allowing its coastguard to fire on foreign vessels in some circumstances, which provoked criticism from Japan. One of four Chinese coastguard vessels that sailed in what Japan sees as its own waters around the islands yesterday was equipped with what appeared to be a large gun, Mr Kato said.

The latest moves near the islands took place as Japan became one of the 58 nations signing up to a Canadian-led declaration opposing arbitrary detentions for political leverage. The declaration is widely seen as targeting China and Iran.

Japan had for years sought to mend its fraught ties with its largest trading partner, and planned to welcome Chinese President Xi Jinping on a state visit last year. The trip was postponed due to the Covid-19 pandemic, with some ruling party lawmakers calling for it to be officially cancelled.

Often caught between the interests of the US, its only military ally, and its near neighbour China, Japan has sometimes been unwilling to criticise China openly.

But Japan did coordinate with Group of Seven nations on a statement last year condemning China's crackdown on Hong Kong.

BLOOMBERG