HONG KONG, Aug. 22 (Xinhua) -- Hong Kong fishing vessel Kai Fung No. 2 reached Hong Kong water on Tuesday evening.

A spokesperson for the Hong Kong Special Administrative Region (HKSAR) government said Chief Executive CY Leung and HKSAR government are pleased to see the safe return of Kai Fung No.2 and seven Diaoyu activists on board.

Fourteen Chinese arrived at the Diaoyu Islands via Kai Fung No. 2 on Aug.15 to assert China's sovereignty over the islands and were subsequently detained by the Japanese coast guard. Seven of them were released and flew back to Hong Kong on Aug. 17.

The spokesperson said that the Diaoyu Islands have been China's territory since ancient times and the Japanese side's detention of Chinese citizens, including Hong Kong residents, was illegal and invalid.

The HKSAR government has attached great importance to the incident and cooperated closely with the Office of the Commissioner of the Ministry of Foreign Affairs in Hong Kong.

The Immigration Department sent officers to Japan on Aug. 15 to join officers of the Hong Kong Economic and Trade Office (Tokyo) in working with the Chinese Embassy and Consulates in Japan to render all practicable assistance to the persons concerned.