Four Chinese ships spent more than 24 hours in what Japan sees as its territorial waters, prompting a Japanese protest to China yesterday at a time when Tokyo has been signalling its desire for a summit.

Relations between the world’s second and third-largest economies have been strained for months, largely because of a dispute over a group of islands in the East China Sea.

But Japanese Prime Minister Shinzo Abe is keen to improve relations and has called for dialogue with China, although he has rejected any conditions on talks.

Chinese ships have previously been in waters near the uninhabited East China Sea islands that are controlled by Japan but claimed by both countries, but they have usually left after several hours.

Japan’s chief cabinet secretary, Yoshihide Suga, told a news conference that Japan had summoned an envoy from the Chinese embassy yesterday to protest “strongly” and demand the ships immediately leave. The ships withdrew at around noon, Japan’s coastguard said. It was the longest stay by Chinese ships in waters near the islands since the dispute flared anew last September, after Japan bought several of theislands from a private owner, angering China.

China’s Foreign Ministry said the Chinese vessels had taken action against a Japanese boat that had entered Chinese territorial waters. China’s State Oceanic Administration said on Wednesday that four coastguard ships were conducting a patrol around the islands.