"China has indisputable sovereignty over the Nansha Islands and the adjacent waters," foreign ministry spokesman Geng Shuang said at a daily briefing on Wednesday.
"Our peaceful construction activities on the Nansha Islands, including the deployment of necessary national defense facilities, are meant to safeguard China's sovereignty and security, which is also the rights a sovereign state is entitled to."
Through efforts by both countries, relations between China and Vietnam have witnessed positive development, Geng said.
"We urge Vietnam to respect China's sovereignty and properly handle the South China Sea issue, promote relations and make them stay on the right track."
Geng's remarks came after Vietnam asked China to withdraw military equipment from the South China Sea.
"Vietnam requests that China, as a large country, shows its responsibility in maintaining peace and stability in the East Sea," Reuters reported.
The Vietnamese statement came after China installed anti-ship cruise missile and surface-to-air missile systems on three fortified outposts in the South China Sea, CNBC reported.
"Vietnam's claim that China is threatening Vietnamese national security is groundless as China's constructions in the South China Sea are defensive and do not target any countries," Chen Xiangmiao, a research fellow at the Hainan-based National Institute for the South China Sea, told the Global Times on Wednesday.
Chen said Vietnam should understand that some countries - especially the US with its increasing presence in the area - are the reason for Chinese military construction.
Vietnam was hyping the China threat theory, encouraging other Asian countries to get tough on China so as to enhance its own bargaining position with Beijing on the South China Sea, Chen said.
"A peaceful situation in the area is not what Vietnam wants to see," Chen said.
Newspaper headline: Foreign ministry urges Vietnam to respect sovereignty