It was a smooth sail for the Hong Kong activists: they managed to skirt government orders and went on without their Taiwanese companion vessel. But their journey to disputed islands in the East China Sea drew to a close with a brush with the Japanese Coast Guard that led to their arrest.

Five activists who were attempting to plant a Chinese flag on the Senkaku islands, known as Diaoyu in Chinese, where arrested along with nine others. According to the Asahi Shimbun, several of the activists jumped into the sea when the Japanese rammed their boat and used a water cannon. A Japanese official denied that the boat was seriously damaged.

China said it would lodge a complaint with Japan for detaining the Chinese nationals. Chinese vice-foreign minister Fu Ying told Reuters that the Foreign Ministry is contacting the Japanese to lodge “solemn representations” over the activists and demanded their safe return. He called on Japan to “immediately and unconditionally release them”. State-run Xinhua news agency accused Japan of escalating tensions “to a new high”.

The Senkaku Islands are the pressure point of relations between Japan, Taiwan and China. Taiwan intercepted activists from the island who were headed to join the Bao Diao, to prevent misconceptions that by allowing them to do so it would be ‘teaming up with’ Hong Kong to defend Chinese claims.