China Tuesday expressed grave concern over a collision between two Japanese patrol boats and a Chinese fishing boat in waters off the Diaoyu islands.

"We have lodged solemn representations with the Japanese side," Chinese Foreign Ministry spokeswoman Jiang Yu said at a regular press conference when asked to comment on the collision, which happened earlier Tuesday.

No injuries were reported from the incident.

Jiang said the Diaoyu islands and its adjacent islets had been Chinese territory since ancient times.

China urged Japanese patrol boats against any so-called law enforcement activities in waters off the Diaoyu islands and refrain from taking any actions that would threaten the security of Chinese fishing boats and their crew, said Jiang.

"We will closely follow the situation and reserve our right to take further action," Jiang said.