Millions of Chinese people vented their anger online yesterday after Japan extended its detention of a Chinese fishing trawler captain, calling for a boycott of Japanese goods and asking the Chinese government to take stronger measures.

And observers of Sino-Japanese relations said the prolonged detention of the captain "severely harms" Chinese people's trust in Japan and undermines the "sound interactions" the two countries have achieved in recent years.

Zhang Zhirong, associate professor of the Institute of International Relations at Peking University, said the incident reflects Japan's lack of respect for human rights.

"The skipper's grandmother died from shock upon learning of the detention. The traditional Mid-Autumn Festival, a time for family reunion, is approaching but the skipper cannot come home," he said, adding that it was "extremely inhumane" for Japan to act in such a way with its hidden political motives.

Chinese Vice Foreign Minister Wang Guangya made solemn representations to the Japanese ambassador to China on Sunday evening, expressing China's deep indignation and protesting Japan's prolonged detention of the Chinese skipper, Zhan Qixiong.

Wang warned that China will take countermeasures if the Japanese side fails to release the Chinese captain immediately and unconditionally, adding that how the situation develops depends completely on the choices the Japanese side makes.

"Japan shall suffer all the consequences that arise," he noted.