Japan has summoned China's ambassador to japan Cheng Yonghua

Japanese protested over Chinese ships and fishing vessels inter in waters that 

Tokyo considered its territorial 

of dispute islets. 

The Japanese foreign mister said. 

The Chinese coastguard ships and fishing 

vessels have sailed in 

the area in what said to be increased assertion of 

jurisdiction over the islets. 

The Japanese Vice foreign Minister 

Shinsuke Sugiyama

 has summoned

 China's ambassador to japan 

Cheng Yonghua to lodge a 

strong protest.