Beijing called in the Japanese ambassador in the early hours yesterday - for the fourth time in five days - over Japan's seizure of a Chinese fishing boat in disputed waters in the East China Sea.
Diplomatic relations between the countries are now at their most tense in more than three years.
State Councillor Dai Bingguo summoned Tokyo's ambassador to Beijing, Uichiro Niwa, 'in the wee hours' yesterday - according to the Chinese Foreign Ministry - to warn against any misjudgment over the incident and demand the immediate release of the Chinese captain and his 14 crew members.
Dai is the highest-ranking Chinese official to intercede since the trawler collided with two Japanese patrol vessels near the disputed Diaoyu Islands on Tuesday. Niwa had already been called in by the Foreign Ministry three times.
'[He] solemnly stated the Chinese government's major concerns and urged Japan not to misjudge the circumstances and to make the wise political choice of immediately returning the Chinese fishermen and their boat,' Xinhua reported.
Niwa gave no indication that his government was preparing to back down.