TOKYO: Chinese and Russian naval forces conducted a joint live-firing exercise using machine guns within Japan’s exclusive economic zone, a sign of their deepening military cooperation, Tokyo said Tuesday.

The incident on Sunday was the first time that Japan’s defense ministry has spotted a live-fire drill by China within its EEZ and disclosed it, according to Japanese media.

Tokyo sees the drill as “part of a move by the two militaries toward strengthening their cooperation,” Japan’s top government spokesman Minoru Kihara said at a Tuesday briefing.

Relations between Japan and China have worsened since Japanese Prime Minister Sanae Takaichi angered Beijing in November with comments about Taiwan.

On Sunday, the Chinese navy’s Luyang III-class missile destroyer was seen conducting the exercise 180 kilometers (110 miles) southwest of the Okinotori island, Japan’s southernmost territory, alongside a Russian naval vessel, officials said.