A Chinese Navy surveillance ship passed through the Tsugaru Strait in northern Japan this week, according to Japan Coast Guard officials.

Although an increasing number of Chinese naval vessels have been operating in the East China Sea near Japan, it was the first time such a ship passed through the strait between Hokkaido and Aomori Prefecture, the officials said.

The surveillance ship Yanbing was cruising 75 km northeast of the Shimokita Peninsula in Aomori Prefecture around 7 a.m. on Wednesday, after passing through the strait heading east, the officials said.

The ship was first spotted by the JCG in the sea near Tsushima Island in Nagasaki Prefecture on May 14. After cruising the sea off Kyushu until last Saturday, the 102-meter vessel headed north through the Sea of Japan, the officials said.

JCG vessels have been shadowing the ship since it was first spotted, the officials said.

The Tsugaru Strait is designed as an international thoroughfare where foreign vessels are allowed to cruise without permission, as long as they do not anchor there.