China urged "relevant country" to respect its sovereignty and stop illegal invasions and construction activities on the Nansha Islands and their adjacent waters, Foreign Ministry Spokesman Lu Kang said Friday.

Lu made the remarks at a press briefing in response to a media report that Vietnam has started dredging work on a reef in the southwestern fringe of the Nansha Islands in the South China Sea.

"We urge relevant country to respect China's sovereignty and rights, stop illegal invasion and construction activities, and not to take actions that could complicate the situation," Lu said.

China has indisputable sovereignty over the Nansha Islands and their adjacent waters, he said.

Lu called on the country to make joint efforts with China for security and stability in the South China Sea region.