Taiwan's navy mistakenly launched a supersonic anti-ship missile from a naval base, killing one person and injuring three, officials say.
A patrol boat was undergoing a drill inspection in Kaohsiung when the Hsiung Feng III missile was fired, Taiwan's Central News Agency (CNA) reported.
It launched in the direction of mainland China, and hit a fishing boat off the Penghu islands, CNA added.
A Taiwanese official said the launch was not "politically motivated".
It came as China celebrates the 95th anniversary of the formation of the Chinese Communist Party.
China considers Taiwan a breakaway province, to be reunited with the mainland, by force if necessary.
There were conflicting reports about the missile's range. The defence ministry said its range was greater than 100km (62 miles), but would not provide exact figures.
The boat's captain, a Taiwanese man, has been killed, defence officials say.
The missile flew about 75km before hitting the boat. Initial findings indicated it did not explode and sank into the sea.
Taiwanese officials did not say how the missile came to be launched, but suggested it could have been due to human error.
'Not politically motivated'
China has claimed sovereignty over Taiwan since 1949, when the two sides split after a civil war, and it has hundreds of missiles pointed towards the island at all times.
Taiwanese President Tsai Ing-wen, who is also head of the military, is currently overseas.
Chen Chung-chi, a spokesman for Taiwan's defence ministry, said: "It is not the case that this is politically motivated, or to create crisis."
It was unclear whether Beijing had been notified directly.
When asked by reporters if the incident would affect relations with Beijing, Taiwanese Vice-Admiral Mei Chia-hsu said the navy had reported it to the island's defence ministry.
He said the case was under investigation and would be handled "accordingly".