Over 70 Taiwanese fishing vessels are heading for two disputed islands in the East China Sea to protest their nationalization by the Japanese government, Kyodo News reported.

The vessels left the port of Yilan in northeastern Taiwan earlier on Monday and are expected to be within 37 kilometers of the islands by 5 a.m. local time on Tuesday, Kyodo said. It had no information concerning further moves by the Taiwanese vessels.

Kyodo said that three Chinese navy ships briefly entered Japanese territorial waters around the islands on Monday morning. Two of the ships were equipped with long-range sonar equipment, according to Japanese coast guard information.

Within a few hours all three left, to join three others on station just outside the territorial waters.

The islands, known as the Senkaku to Japan and Diaoyu to China, have been at the center of a dispute recently that has triggered violent anti-Japanese protests across China and caused Japanese companies to suspend operations in China.

Both Taiwan - to which the pre-1949 Chinese government moved - and China reject Japan’s claims to the islands, which were controlled by the United States after World War II and granted to Japan in 1972.

Japan claims that China and Taiwan only began to take an interest in the islands in the 1970s, when evidence was discovered of major subsurface resource deposits in their territorial waters.

The issue flared up after Japan nationalized three of the five islands two weeks ago, which previously belonged to a private owner.

Beijing and Tokyo cannot agree on a maritime border in the economic zones around the islands. Japan claims it has occupied the islands since 1895, while Beijing says Japanese charts dating back to 1783 show the islands as Chinese territory.