SUAO, Taiwan (AFP) — Dozens of Taiwanese fishing boats yesterday set sail for disputed East China Sea islands that are also claimed by China and Japan and have sent tensions between the two Asian powers soaring.

The fishermen aim to highlight Taiwan's claim over the uninhabited islands — known as Diaoyu in China but Senkaku in Japan — which lie 400 kilometres (250 miles) from the Okinawan capital of Naha and 200 kilometres from Taiwan.

The islands, which are administered by Japan, lie on vital shipping lanes and are believed to be located near potentially rich gas fields.

The flotilla of 78 fishing boats flying Taiwan flags and brandishing demonstration signs left Suao, a port in northeast Taiwan, at 0700 GMT. They are expected to arrive around dawn today.

Once there, they plan to sail inside Japan's 12-nautical-mile territorial zone surrounding the disputed islands.

The numbers of vessels could swell, according to the activist group which organised the protest sail.

"I'm certain there will be more based at other fishing ports to join us," Lin Cheng-an, a spokesman for the Suao Fishermen's Association, told AFP.

Chen Chun-sheng, the head of the Suao association, said at the weekend: "Diaoyutai has been our traditional fishing ground for centuries. We pledge to use our lives to protect it or we'd disgrace our ancestors."

The departing boats carried signs written in Chinese characters reading "Diaoyutai belongs to Taiwan" and "Fighting for fishing rights for survival".

Taiwan's coastguard sent at least 10 patrol boats alongside the fishing vessels, an official with the Coast Guard Administration said.

On Sunday, more than 1,000 slogan-chanting Taiwanese activists and their supporters rallied outside the de facto Japanese embassy in Taipei, calling for a boycott of Japanese goods.

Tensions have mounted after Japan announced earlier this month that it had completed a planned purchase of some of the islands, prompting Taiwan to recall its envoy to Tokyo and triggering mass protests in China.