Hong Kong (CNN) -- Dozens of fishing boats and 12 coast guard ships from Taiwan briefly entered waters close to a disputed island chain in the East China Sea, Japan's Coast Guard said on Tuesday.
The Coast Guard said the vessels had left Japanese territorial waters by noon local time after it issued a warning and fired water cannons at the ships. It said the Taiwan coast guard vessels fired water from high-pressure hoses in return.
It added that 10 Chinese surveillance ships were in the area but none had strayed into waters regarded by Japan as its territory.
The long-running dispute over the islands has flared up in recent months, triggering anti-Japanese protests in China.
Taiwan, China and Japan all claim ownership of the islands.
Taiwan news agency CNA said that up to 100 fishing boats, escorted by 10 coast guard ships, were making the voyage to assert local fishermen's rights to operate in the waters.
It said the fishing boats came as close as three nautical miles to the islands before turning away.
Wang Jinn-wang, head of Taiwan's Coast Guard Administration, was quoted as saying the flotilla was "the biggest ever action" to support Taiwan's sovereignty over the islands.
CNA said the island chain lies 100 nautical miles northeast of Taiwan.
Earlier this month, the Japanese government bought the disputed islands -- known as Senkaku in Japan and Diaoyu in China and Taiwan -- from the Japanese family that owned them for 2.05 billion yen (US$26.2 million).
The move infuriated China.
Protests erupted across dozens of Chinese cities, forcing the closure of a number of Japanese businesses and factories as residents railed against anything representative of Japan or its people.
While Taiwan, which Beijing regards as a breakaway province, has long been a claimant in the Diaoyu/Senkaku dispute, the self-governing island has seldom rigorously advanced its claims because of an unwillingness to risk its good relationship with Japan, said Alan Dupont, a strategic analyst at the University of New South Wales in Sydney.
He said Taiwan's decision to become more assertive was a response to recent action taken by China and Japan, as well as concerns over access to fishing and marine resources.
"Under the Law of the Sea, you have to demonstrate an ongoing interest in the islands over a period of time. It rewards countries that assert their claims," he said.
China says its claim to the islands goes back hundreds of years.
Japan says it saw no trace of Chinese control of the islands in an 1885 survey, so formally recognized them as Japanese sovereign territory in 1895.
Japan then sold the islands in 1932 to descendants of the original settlers. The Japanese surrender at the end of World War II in 1945 only served to cloud the issue further.
The islands were administered by the U.S. occupation force after the war. But in 1972, Washington returned them to Japan as part of its withdrawal from Okinawa.
Beijing and Taipei both claim they inherit China's historic sovereignty over the island. Taiwan is governed by the nationalist Kuomintang party that fled to Taiwan after losing to China's communists in 1949.
"The islands get subsumed in the long-running dialogue about reunification," said Dupont.
"It is one situation where strategic objectives are in sync."
Dupont also said Taiwan's protest would be an unwanted complication for the U.S. as it tries to strengthen its relationships in Asia to counter China's rising power.
"It has two of its allies involved in disputes not only with China but also with each other over the same rock."