Three Chinese government ships sailed into waters around disputed islands controlled by Tokyo on Saturday,
the Japanese coastguard said.
The maritime surveillance vessels entered the 12-nautical-mile zone off Uotsurijima, one of the Senkaku islands, which China calls the Diaoyus, in the East China Sea shortly after 9:30 am (0600 IST), the coastguard added.
Three Chinese ships sail into disputed islands, claims Japan
Ships from the two countries have been involved in a stand-off as Beijing and Tokyo jostle over ownership of the strategically important and resource-rich islands.
A territorial row that dates back four decades reignited last September when Tokyo nationalised three islands in the chain, in what it said was a mere administrative change of ownership.
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