TOKYO鈥擜 Chinese naval ship sailed into waters surrounding disputed East China Sea islands for the first time early Thursday, prompting Tokyo to summon the Chinese ambassador to protest, the Japanese government said.
Russian naval ships were also seen in the area around the same time, according to local media.
鈥淎round 00:50 am (1530 GMT Wednesday), a Chinese naval vessel entered our nation鈥檚 contiguous waters surrounding the Senkaku Islands,鈥� the Japanese foreign ministry said in a statement.
Japan administers the uninhabited isles under that name while China also claims them and calls them the Diaoyu islands.
READ: Japan to deploy troops near disputed East China Sea islands | China Coast Guard building up fleet
Relations between Japan and China deteriorated in 2012 when Tokyo 鈥渘ationalized鈥� some of the islands.
Since then, the two largest Asian economies have taken gradual steps to mend fences but relations remain tense.
Japanese Vice Foreign Minister Akitaka Saiki summoned Chinese ambassador Cheng Yonghua around 2:00 am to lodge a protest.
Saiki 鈥渆xpressed grave concerns and protested, while demanding the ship immediately leave our nation鈥檚 contiguous zone,鈥� the ministry statement said.
Japanese diplomats and defense officials could not be reached immediately for further comment.
During his meeting with Saiki, Cheng claimed the Chinese frigate was allowed to sail in the waters, Kyodo 黑料社 said, citing an unnamed source.
The frigate left the zone at about 3:10 am, according to major Japanese media, including Kyodo and national broadcaster NHK.
Chinese coast guard vessels routinely travel around the disputed islands, but this was reportedly the first time a Chinese navy ship has been spotted.
Three Russian military vessels were also seen in the waters around the disputed islands around the same time, Japanese media said.
The Russian ships entered the area around 9:50 pm Wednesday and left around 3:05 am Thursday, Jiji Press said, adding that Russian naval ships have entered the waters before.