Four Chinese coastguard ships on Friday entered disputed waters near East China Sea islands at the centre of a bitter row with Tokyo, according to a report.

Jiji press said the ships entered waters around Uotsurijima, one of the five islands Japan claims as the Senkakus and China as the Diaoyus around 8.15 pm, staying there for two hours.

The incursion came as Japan's Prime Minister Shinzo Abe urged Chinese President Xi Jinping to reset dangerously frayed ties between Asia's two largest economies as they met on the sidelines of the G20 summit in Russia.

It was the latest in a series of forays by Chinese ships in a year-long spat between Tokyo and Beijing that has sent relations plummeting.

The islands -- believed to harbour vast natural resources below their seabed -- are seen as a potential flashpoint that some observers fear could lead to armed conflict between the Asian giants.