Tsang Kin-shing, one of the activists, could not hide his euphoria as he counted down their approach by satellite telephone to Hong Kong.

"One metre left … put down the ladder … let's go into the water," he said, before the group sang the national anthem.

"We have all kinds of flags - communist [with the hammer and sickle], national [with five stars] and Hong Kong's flag," Tsang said.

Captain Yeung Hong, also an activist, said: "Every hour of the voyage was a surprise to me, a surprising victory."

Aside from placing the national flag to claim Chinese ownership of the islands, the group also planned to install Chinese-made televisions or radios on the islands and to dismantle a Japanese lighthouse.

The group had sailed through stormy weather, and endured dangerous harassment from Japanese ships.

In the last 16 kilometres, the fishing boat was hit by at least one Japanese vessel, disrupting its steering. A Japanese ship also fired a water cannon at the boat, hampering the crew's visibility.

"They [the Japanese] tried to create a dangerous situation in which we might collide with them. But we made use of our computer-assisted navigation system," Tsang said.

Once within 80 kilometres of the Diaoyus, the boat was tailed by five Japanese ships, and warned in both Japanese and Putonghua.

The Japanese escort rose to nine ships when the boat was 32 kilometres away. At one point, the Kai Fung had to sail through a narrow space between two Japanese vessels.

At around 4.30pm, seven of the activists disembarked onto the island, and were met by more than 30 Japanese security personnel.

Activist Lo Chau cried when they docked. "We have waited for more than a decade, and I can't help but burst into tears," he told Phoenix TV, which had a reporter and cameraman on board.

The other activists were Koo Sze-yiu, Wong Fah-man, Lo Chung-cheong, Ng Shek-yiu from Macau and mainlander Fang Xiaosong.