Japanese Chief cabinet Secretary Yoshihide Suga (photo by AFP)
Japan has accused China of intruding into what Tokyo considers as its territorial waters in East China Sea, pledging to respond firmly but calmly to the alleged trespassing. 
Chief Cabinet Secretary Yoshihide Suga said on Monday that Japan would continue to urge China not to escalate the dispute which has drawn in trans-regional powers, such as the US.
Suga claimed that a total of 14 Chinese vessels had entered "contiguous waters" at the weekend, 12 of which had remained in the area early on Monday.
He said several Japanese agencies, including the Coast Guard, would cooperate to deal with the situation. Government sources said the Coast Guard has beefed up its patrols in the region over the weekend.
Japan has so far issued multiple protests to Beijing, including one which was made on Friday over the discovery of what Tokyo calls the installation of a radar system on a Chinese offshore gas platform.
The Japanese Coast Guard ship PLH02 Tsugaru (background) is seen in this file photo with a Philippine Coast Guard boat (C) during an annual joint exercise in the waters off Manila Bay on July 13, 2016. (AFP)
Tokyo said it discovered the radar facility along with surveillance cameras installed on one of China's gas-drilling platforms in June.
A Foreign Ministry spokesman called for the “immediate removal of the equipment,” saying Japan “cannot accept” the radar.
Tokyo is locked in a separate territorial row with Beijing on an uninhabited yet strategically important island group in the East China Sea.
Earlier this month, China’s Defense Ministry said in a statement that two Japanese jets had taken “provocative” actions near a pair of Chinese jets in the East China Sea on June 17.
The Chinese aircraft had been on routine patrol when they met the Japanese jets and responded “decisively” to the provocations, the statement said.