Tokyo says China coast guard vessel 2204, seen here in November 2022, appeared to be armed with a deck-mounted machine gun when it entered Japanese territorial waters in the East China Sea, Friday, Feb. 24, 2023. (Japan Coast Guard)

CAMP FOSTER, Okinawa — Japan lodged diplomatic protests with China over alleged intrusions by the China coast guard into waters Japan claims as its territory around islets in the East China Sea, according to Japan’s Foreign Ministry.

Four Chinese coast guard ships passed the 12-mile territorial limit around the Senkakus between 10:15 a.m. and 10:40 a.m. Friday, a Japanese coast guard spokesman told Stars and Stripes by phone Monday. All four vessels left those waters without incident by 12:15 p.m., he said.

Japan’s Foreign Affairs Ministry lodged complaints with the Chinese Embassy in Japan and with the Chinese government in Beijing on Friday, a Ministry of Foreign Affairs spokesman told Stars and Stripes by phone Monday.

“This is unacceptable,” the spokesman said. “We asked them to leave the area immediately.”

Some government officials in Japan are required to speak to the media only on condition of anonymity.

A pair of Chinese coast guard vessels approached Taisho Island in the Senkakus from the north and entered the 12-mile limit at 10:15 a.m. and 10:20 a.m., according to the Japanese coast guard spokesman. Two more vessels entered from the southeast of Kuba Island at 10:32 a.m. and 10:40 a.m.

One of those ships appeared to be armed with a deck-mounted machine gun, the spokesman said.

The Chinese vessels were met by a larger contingent of Japanese coast guard ships, the spokesman said. He declined to provide the exact number.

They warned the Chinese vessels to leave the area using radio and electronic message boards, he said.

There was no contact between the vessels, the spokesman said. It remains unclear why the ships entered Japan’s territorial waters. No Japanese fishermen were operating in the area, which is usually the case when Chinese vessels appear, the spokesman said.

The incidents marked the fifth and sixth times this year that Chinese coast guard vessels intruded into Japan’s territorial waters, the spokesman said. The last incident occurred Jan. 30.

There is growing concern in Japan that China is stepping up military activities in the region, Japan’s Chief Cabinet Secretary Hirokazu Matsuno said earlier this month.

Japanese lawmakers in December approved a record defense budget of about $51.4 billion for fiscal year 2023 that emphasized counterstrike capabilities and strengthened standoff air and missile defense.

The Senkakus are 105 miles east of Taiwan. The islets, whose surface area amounts to about 2½ square miles, are also claimed by China and Taiwan, which refer to them as Diaoyu Dao and Diaoyutai, respectively. The surrounding area is said to contain a wealth of natural resources, including fish, oil and natural gas.