China’s coast guard expelled Japanese ships that illegally entered China’s territorial waters around the Senkaku Islands on Monday, a move experts said was the right one in safeguarding China’s sovereignty and territorial integrity, adding that it displayed the coast guard’s capabilities.

Five Japanese ships, including the Shinsei Maru, illegally entered China’s territorial waters around the Senkaku Islands on Monday, and China Coast Guard vessels took necessary management and control measures and warned them away according to the law, said spokesperson Gan Yu in a statement on Monday.

The Diaoyu Islands and affiliated islands are China’s inherent territory, and Japan is in no position to make irresponsible comments about China’s maritime law enforcement in waters under Chinese jurisdiction, Gan said.

“We call for the Japanese side to immediately stop all illegal activities in this region and make sure incidents like this never happen again,” the spokesperson said.

Gan’s statement came after Japanese media reports on Monday said that the 997-ton Shinsei Maru survey boat carrying Yoshitaka Nakayama, mayor of Ishigaki, Okinawa Prefecture, and researchers from Tokai University “conducted a marine survey” around the Senkaku Islands.

The Japanese researchers flew a drone several times to within 300 meters of the Senkaku Islands and took images of the area, Japan’s Yomiuri Shimbun reported.

A China Coast Guard vessel approached the Shinsei Maru in the process, leading to a “diplomatic protest” from the Japanese government to the Chinese side, the Japanese report said.

China’s coast guards routinely patrol waters around the Senkaku Islands, and any foreign vessels trespassing into Chinese territorial waters will be expelled according to China’s Coast Guard Law, a Beijing-based military expert who requested anonymity told the Global Times on Monday.

With the routine patrols, daily training and additional vessels entering service, the China Coast Guard is fully capable of safeguarding national sovereignty, security and maritime interests, the expert said.

Japan should not again hype the Senkaku Islands dispute, because this will only worsen bilateral ties at a time when Japan has broken away from its self-defense-only principle and is preparing offensive weapons and planning to interfere in the Taiwan question, which is an internal affair of China, the expert said.