The Defense Ministry on Friday criticized Japanese fighter jets that disturbed routine patrols by Chinese aircraft over the East China Sea amid lingering tensions over the Diaoyu Islands.

Tokyo also ramped up its hardline stance as Japanese Prime Minister Shinzo Abe said on Friday there was "no room for negotiation" on the row.

Analysts said Tokyo is now keen to test Beijing's bottom line by flaring up military confrontation, and to seek more bargaining chips for future talks.