Chinese ships enter Japan territorial waters off Aomori Pref.

Two Chinese coast guard ships briefly entered Japanese waters Friday off the northeastern prefecture of Aomori, the first Chinese government ships spotted in this area since July 2017, the Japan Coast Guard said.

A patrol vessel of the Japan Coast Guard identified at around 2:40 a.m. two Chinese ships entering Japanese territorial waters off Cape Tappi in Aomori Prefecture, located in the Tsugaru Strait, which separates the Japanese main islands of Honshu and Hokkaido.

The ships left the waters at around 3:15 a.m. after the Japan Coast Guard warned them via radio, however, they re-entered Japanese waters off Cape Oma three and a half hours later before eventually exiting the area around 7:45 a.m.

Under the U.N. Convention on the Law of the Sea, vessels of every country have the right of innocent passage to sail through territorial waters as long as they do not harm the safety of the coastal countries.

Chinese vessels have frequently entered Japanese territorial waters around the Senkaku Islands in the East China Sea, a group of uninhabited islets controlled by Japan but claimed by Beijing, which calls them Diaoyu.