Japan's new annual defence report issued on Tuesday has expressed strong concern over China's increased activities in the South and East China Seas, calling them dangerous.
The report cites China's rapid and large-scale reclamation of reefs in the disputed Spratly Islands in the South China Sea, Japan's NHK news portal reported.
It calls China's increased maritime activity in the South and East China Seas a dangerous act that could lead to an unforeseen incident.
The report also mentions China's development of a new gas field in the East China Sea.
It says Japan has confirmed the construction work and repeatedly issued protests demanding the work be suspended.