UNITED NATIONS (AP) -- China and Japan traded angry accusations in a late-night spat over a small group of islands in the East China Sea that both claim.

It started when Chinese Foreign Minister Yang Jiechi accused Japan of “grossly violating” Chinese sovereignty by its purchase of the islands. He pronounced the moves by Japan as “totally illegal and invalid” during his address late Thursday to the U.N. General Assembly.

The dispute over the islands, called Diaoyu by China and Senakaku by Japan, has raised tensions between them to their highest in years and sparked violent anti-Japan protests in China.

Yang said, “China strongly urges Japan to immediately stop all activities that violate China’s territorial sovereignty” and take concrete actions to correct its “mistakes.”

Japan’s Deputy Ambassador Kazuo Kodama seized on his country’s right of reply at the end of the assembly session, and restated that Japan has every right to the land.

“There is no doubt that the Senakaku islands are clearly an inherent territory of Japan based on historical facts and international law,” Kodama said. “There is no issue of territorial sovereignty to be resolved.”

China’s U.N. Ambassador, Li Baodong, then accused Japan of having an “obsolete colonial mentality.”

Japan’s government says the islands’ purchase, from a private Japanese citizen this month, was intended to help manage the dispute.

Japan administers the islands, and like China, is adamant they are its territory.