A Chinese man who tried to fly a hot-air balloon hundreds of kilometres to islands disputed between Beijing and Tokyo was rescued by Japan's coastguard after ditching in the sea, an official said Thursday.

The 35-year-old took off from China's Fujian province on Wednesday morning in an attempt to land on one of the Tokyo-controlled islands, the Japan Coast Guard official said.

It was an ambitious goal -- hot-air balloons travel largely at the mercy of the wind, and the islands are tiny specks in the East China Sea 359 kilometres (223 miles) away from the take-off point.

They are hotly disputed between Beijing, which regards them as its territory and calls them Diaoyu, and Tokyo, which calls them Senkaku. Tensions have at times reached feverish heights.

In the event the pilot sent a request for help several hours into his flight and ditched in the sea, with a Japanese rescue helicopter picking him up 22 kilometres south of his goal, the official said.

The man, who was unhurt, was handed over to a Chinese patrol ship outside Japanese territorial waters, he added.

Photos distributed by the Japan Coast Guard showed a striped, multicoloured balloon drifting half-deflated in the steely blue waters.

Reports identified the man as Xu Shuaijun, a balloonist who in 2012 became the first man to pilot a hot-air balloon over northeast China's Bohai Bay.

On his verified account on Weibo, a Chinese version of Twitter, Xu posted a short message declaring that he had been returned safely to the city of Fuqing in Fujian province.

"I have returned safely," Xu wrote. "Thanks everyone for your concern."

His supporters wrote back with words of support, with many declaring him a "hero" who had done well even if he had fallen short of his target.

"So awesome!" one user wrote. "What innovative thinking and action!"

"It's enough that you came back safely," wrote another. "Brother Xu, your countrymen are proud of your pioneering act!"

Xu did not post any further details on his voyage and did not immediately respond to a request by AFP for comment.

But in two September microblog postings, he excitedly made note of his plans.

In one he shared a photo of a red Chinese flag with islands in the background. "I got some expert advice today, and am now full of meteorological knowledge! I'm flying to the Diaoyu Islands! Be Chinese with attitude."

In another, he posted what appeared to be a map of his planned route, with a bright yellow line drawn between the Fujianese coast and the islands. He declared the mission "the most difficult in the history of hot air balloon flight".

"Just a balloonist"

Beijing declined to acknowledge any Japanese role in his rescue. Foreign ministry spokesman Qin Gang told reporters that a "Chinese coast guard vessel patrolling in waters of the Diaoyu islands learned that one Chinese balloonist fell into the water".

"The coast guard vessel came to the waters where the accident took place to help the balloonist and the relevant person has been rescued and transferred to the Chinese side," he said at a regular briefing.

"I just want to emphasise that this person is just a balloonist," he added.

Some attempts by activists from both sides to land on the islands have been blocked, but in 2012 about a dozen members of a right-wing Japanese group swam ashore from a 20-boat flotilla. Earlier, 14 pro-China activists sailed to the islands from Hong Kong on a similar trip.

Regional tensions rose in late November when China abruptly declared a new Air Defence Identification Zone over the East China Sea, including the disputed islands.

Chinese state-owned ships and aircraft have approached them dozens of times to assert Beijing's territorial claims, especially since Japan nationalised some of the islands in September 2012.

Tensions between the two countries rose further last week after Japanese Prime Minister Shinzo Abe visited Tokyo's controversial Yasukuni war shrine.

The shrine honours several high-level officials executed for war crimes after World War II, and serves as a reminder of Japan's 20th century aggression against China and other Asian nations.