China is on alert after Japan dispatched fighter jets to airspace over the East China Sea, a Foreign Ministry spokeswoman said Tuesday.

Hua Chunying made the remarks at a daily news briefing. Media reports say Japan's Air Self-Defense Force sent F-15 fighter jets to the area on December 22 to intercept a Chinese marine surveillance plane bound for the Diaoyu Islands in the East China Sea.

"As far as I know, China's marine surveillance plane you mentioned has been conducting routine patrols in airspace over the East China Sea," she said in response to a journalist's question.

"The Chinese side is highly concerned with, and alert to, Japan sending the Air Self-Defense Force jets," said the spokeswoman, adding that China had lodged solemn representations to Japan over the issue.

"The Chinese side will pay close attention to Japan's intentions," she added.

(Xinhua News Agency December 25, 2012)