A Japanese summary court on Sunday authorized prosecutors to extend by 10 days the detention of the captain of the trawler which was involved in a collision incident with Japan Coast Guard ships earlier this month to Sept. 29.

The decision was made by the Ishigaki summary court, Okinawa Prefecture, as the original detention of the skipper, Zhan Qixiong, was due to expire Sunday.

Zhan's trawler collided with two Japanese Coast Guard patrol vessels off the Diaoyu Islands in the East China Sea on Sept. 7. He was later held by Japanese authorities for allegedly " obstructing public duties." The 14 fishermen aboard and the trawler were returned by Japan on Sept. 13.

China has repeatedly expressed opposition to the illegal detention and demanded an immediate release of the captain.

Foreign Ministry spokesman Ma Zhaoxu said in a press release Sunday China will take "strong counter measures if Japan insists on its mistakes" in issues concerning detaining a Chinese trawler captain.

China has already suspended ministerial and higher level exchanges with Japan as well as bilateral negotiations on increasing air routes between their countries. Chinese visitors to Japan will also scale down, foreign ministry said after the latest development on Sunday.

Hundreds of Chinese gathered outside Japanese diplomatic residences across the country on Saturday to protest Japan's seizure of the captain as sirens wailed to mark the 79th anniversary of Japan's invasion.

After the trawler and its captain were seized, Chinese surveillance ships have been dispatched to safeguard China's rights and interests in Chinese waters.