Around 15 protesters shouted anti-Japanese slogans, burned Japanese flags and called for the Japanese to leave the islands, which are claimed by China, Japan and Taiwan.
“We are extremely angry,” said Tsang Kin-shing, who was among a group of Hong Kong-based activists who landed on the islands last month and raised the Chinese and Taiwanese flags.
Tokyo agreed to purchase the islands, known in Japan as Senkaku and in China as Diaoyu, for 2.05 billion yen (US$26 million) on Monday, prompting Beijing to send two patrol ships to the area.
“Japan is using the issue of Diaoyu Islands to reignite public sentiment, so I believe all Chinese people are angry,” Tsang told reporters.
He said the group that made the successful landing on the islands last month was preparing another trip from Hong Kong.
“Our ship will leave any time,” he said.
Chinese Premier Wen Jiabao has said the islands were “an inherent part of China’s territory” and vowed his country would “never ever yield an inch” on its sovereignty.
The islands lie in a strategic shipping area with valuable mineral resources thought to be nearby.