BEIJING -- 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 Saturday 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.