Chinese coast guard ships were spotted Monday near the Japan-controlled Senkakus in the East China Sea, marking a new record for the number of days in a year that Chinese vessels have been seen near the uninhabited islands, the Japan Coast Guard said.
Four Chinese ships were spotted in the "contiguous zone" outside Japanese waters, the coast guard said, adding that Chinese vessels have now been observed near the islands, claimed by Beijing, for 283 days this year and also for the 57th day in a row.
China has ratcheted up pressure on Japan by sending its vessels into or near Japan's territorial waters around the islands.
Last month, Chinese coast guard ships entered Japanese territorial waters near the Senkakus for a record length of time, drawing objections from Tokyo.
"We take the repeated entry into the contiguous zone and intrusions into Japanese territorial waters very seriously, and have issued warnings through our coast guard ships as well as making strong protests through diplomatic channels," Chief Cabinet Secretary Katsunobu Kato said in a news conference on Monday.
"We will remain vigilant and, coordinating among the relevant ministries, continue to gather information and maintain surveillance over the Senkaku Islands in order to protect our territory," the top government spokesman said.
The islets in the resource-rich sea are also claimed by Taiwan.