TAIPEI: A boat carrying Taiwanese activists headed for disputed Japanese-controlled islands turned back Thursday after coastguard vessels from the two sides converged and duelled with water cannon.

The boat, carrying seven people including four Taiwanese activists, abandoned a plan to land on the East China Sea islands after being blocked by Japanese coastguard vessels as it sailed within 17 nautical miles.

"We fired water cannon at each other," Taiwanese coastguard spokesman Shih Yi-che said of the confrontation.

The disputed islands, in an area where the seabed is believed to harbour valuable mineral reserves, are known as Senkaku in Japanese and Diaoyu in Chinese. Both China and Taiwan claim them.

The incident came at a time of growing regional concern over the intensified standoff over the islands between China and Japan, with both Beijing and Tokyo recently scrambling fighter jets to assert their claims to the area.

The Japanese coastguard confirmed that it took action after encountering the Taiwanese vessel.

"Our patrol boat carried out restrictions on the vessel such as blocking its path and discharging water," it said in a statement.

"The vessel left our country's contiguous zone at around 1:30 pm (0430 GMT) and continued sailing west-southwest away from the Senkakus."

The activists, who set off in the early hours and were expected to return to Taiwan at about 7:00 pm (1100 GMT), had hoped to place a statue of the Goddess of the Sea on the islands, a gesture to protect Taiwanese fishermen in the area.

They had also intended to "maintain sovereignty" in defiance of Japan's control, said Hsieh Mang-lin, the Taiwanese chairman of the Chinese Association for Protecting the Diaoyutais (Diaoyu Islands).

Japanese broadcaster NHK reported that Taipei had dispatched six patrol boats to "monitor" the ship, adding it was the same one that had entered waters off the islands in July.

Taiwan's coastguard denied it was an organised flotilla, but said four of its vessels on routine patrols in the area had protected the vessel.

"The coastguard will protect our people's voluntary actions to defend the Diaoyu islands. Coastguard vessels will go wherever the fishing boat is... to defend our sovereignty and protect our fishing rights," it said in a statement.

Coastguard vessels from Japan and Taiwan also exchanged water cannon barrages in September after dozens of Taiwanese boats were escorted by patrol ships into the islands' waters.

Previous activist landings have resulted in the arrest and deportation of those setting foot on what Japan says has been its indisputable territory for more than a century.

The rocky island outposts have been the scene of a diplomatic tussle between Japan and China for months.

Japan's government nationalised three of them in September by taking them out of private Japanese ownership.

Since then, Beijing has repeatedly sent government ships into the waters. In December a Chinese government plane overflew them, leading Japan to scramble fighter jets.

Earlier this month both militaries had jets in the area and Japanese newspapers have reported that Tokyo is mulling allowing its pilots to fire warning shots.

While most commentators believe Asia's two largest economies will find some way to work around the problem, which has rattled relations for decades, some are warning that a mis-step could lead to armed confrontation.