Fears grew Sunday of Tokyo’s relations with Beijing entering a downward spiral, after China warned its citizens not to travel to Japan in the near term, following Prime Minister Sanae Takaichi’s comments that Japan could intervene militarily if China uses force against Taiwan.

The warning by Beijing late Friday was the first significant retaliatory move by China in an escalating row that is threatening to become the worst flare-up in ties since 2012, when the two countries’ dispute over the Senkaku Islands triggered waves of anti-Japanese protests in China.

“Recently, Japanese leaders have made blatantly provocative remarks regarding Taiwan, severely damaging the atmosphere for people-to-people exchanges between China and Japan and posing significant risks to the personal safety and lives of Chinese citizens in Japan,” China’s Foreign Ministry said in a statement late Friday.