The officials, speaking after a more hawkish Japanese Prime Minister – Shinzo Abe – took office, were responding to Japan sending jet fighters several times in the past two weeks to intercept Chinese patrol planes approaching airspace above the islands.
The situation in the volatile East China Sea region has severely strained relations between Beijing and Tokyo.
"We will decisively fulfil our tasks and missions while co-ordinating with relevant departments so as to safeguard China's maritime law enforcement activities and protect the country's territorial integrity and maritime rights," a Chinese defence ministry spokesman said.
Japan's defence ministry has acknowledged scrambling F-15 jets on several occasions in recent weeks to intercept Chinese marine surveillance planes approaching the islands, called the Diaoyu in Chinese and the Senkaku by Japan.
It says a Chinese aircraft breached what it considers Japanese airspace for the first time on December 13.