The head of Taiwan's main opposition party left for Japan Sunday on a goodwill visit despite a sovereignty dispute over islands in the East China Sea.

Su Tseng-chang, chairman of the China-sceptic and Tokyo-friendly Democratic Progressive Party (DPP), was making his first foreign trip since being elected party leader last May.

"We give priority to Japan, as it is a crucial neighbouring country of Taiwan and has maintained a longstanding friendly relationship with Taipei," the party said in a statement.

China, Taiwan and Japan dispute the sovereignty of the islands known as the Diaoyu islands in Chinese and Senkaku in Japanese.

Last month a boatload of Taiwanese activists protected by coastguards sailed to waters off the islands. Coastguards from the two sides converged and duelled with water cannon.

The boat, carrying seven people including four Taiwanese activists, gave up a plan to land on the islands.

Intensified friction over the islands between China and Japan has seen both sides recently scrambling fighter jets to assert their claims.

Su may meet Japanese political figures and scholars to discuss "a wide range of topics" during his five-day visit, said party spokesman Lin Chun-hsien.

Lin declined to say if the discussions would touch on the sensitive islands dispute.

He said Su currently has no plans to meet Shintaro Ishihara, a right-wing activist and former Tokyo governor who last year tried to buy the disputed islands to assert Japan's claim.

Japan colonised Taiwan from 1895 to 1945.