China on Tuesday expressed "serious concern" and "strong discontent" over a Japanese coastguard vessel's collision with a Taiwan fishing boat in the East China Sea.

"The Diaoyu Island has been Chinese territory since ancient times. China holds indisputable legal evidence of ownership," Chinese Foreign Ministry spokesman Qin Gang said here at a routine briefing.

According to media reports, a fishing boat from China's Taiwan Province sank early Tuesday morning after colliding with a Japanese coastguard patrol boat about 9 km south of the Diaoyu Islands.

"We demand the Japanese government stop illegal activities around the Diaoyu Islands so as to prevent incidents of this kind from happening again," Qin said.