A maritime research ship of National Taiwan University intruded into Japan's territorial waters near the disputed Senkaku islets in the Each China Sea early Friday, ignoring a warning from a Japan Coast Guard vessel, JCG officials said.

The 794-ton, 50-meter ship at 5:25 a.m. entered the waters 22 km southeast of Uotsuri Island of the islet chain, which is under Japan's control but also claimed by Taiwan and China.

Despite the warning from the JCG patrol ship Hateruma, the research ship stayed in Japanese territorial waters for three hours, according to coast guard officials in Tokyo.

When the Hateruma's crew tried to ascertain by radio the purpose of the vessel's trip, the Taiwanese replied that they were collecting seawater for research.

The Hateruma demanded the ship immediately leave Japan's territorial waters, informing it that research activities without advance notice and the consent of the Japanese government are not allowed. However, the Taiwanese ship failed to respond further and left the territorial waters around 8:20 a.m., the coast guard officials said.

The intrusion follows a diplomatic row between Taiwan and Japan on June 16, when a private protest boat and nine Taiwanese patrol boats entered Japan's territorial waters near Uotsuri Island to protest the accidental sinking on June 10 of a Taiwanese fishing boat.

The fishing boat sank following a collision with the JCG ship Koshiki off the island, drawing fierce protests from the Taiwanese government and public.