Sino-Japanese relations deteriorated sharply last month after Japan detained a Chinese trawler captain whose boat collided with Japanese patrol ships near the disputed islands -- called Senkaku in Japan and Diaoyu in China.

Japanese Prime Minister Naoto Kan's comments to parliament were followed by remarks from Foreign Minister Seiji Maehara that China's actions in the dispute were "extremely hysterical," underlining the difficulty of putting a quick end to the spat.

Kan has come under fire domestically for appearing to cave in to Chinese demands to release the captain. On Saturday, thousands marched in Tokyo to assert Japan's claim to the rocky isles, which are near potentially huge oil and gas reserves in the East China Sea.

"Regarding the Chinese protests against Japan on the 16th and 17th, we will tell the Chinese authorities that it is regrettable and ask them to ensure the safety of Japanese nationals and Japanese companies in China," Kan told a parliamentary panel.

"Both sides need to work hard (on the matter) in a calm manner," Kan added.

Reuters