BEIJING - A national defense spokesman on Thursday reiterated China's sovereignty over Ren'ai Reef in the South China Sea, adding that the illegal grounding of a Philippine vessel on the reef represents encroachment on China's territorial sovereignty.

China's resolution and will to safeguard its territorial sovereignty is unswerving, Geng Yansheng, spokesman for the Ministry of National Defense, said at a press conference.

China has indisputable sovereignty over the Nansha Islands, which include Ren'ai Reef, and their adjacent waters, Geng said, adding that Chinese naval patrols in the area are justifiable.

In 1999, a Philippine warship was grounded on Ren'ai Reef. China has repeatedly asked the country to retrieve the ship, but the Philippines has ignored China and continued to illegally occupy the reef, Geng said.

He said the Philippine's act violates the Declaration on the Conduct of Parties in the South China Sea.

Geng said the Philippines' claim that Chinese vessels have threatened to cut off supplies of water and food for Philippine military staff at the reef is groundless.

China firmly opposes any action that could amplify or complicate the situation, Geng said.