Vietnam has undisputable sovereignty over the Truong Sa (Spratly) and Hoang Sa (Paracel) archipelagoes, Foreign Ministry spokeswoman Nguyen Phuong Nga said Friday.
"Vietnam requests China to stop and not to repeat activities violating Vietnam's sovereignty," Nga said at a press briefing in Hanoi.
She made the statement in response to a question on recent information released by the Xinhua news agency.
The Chinese news agency on April 3 said China's Hainan province defined Cay Island, which belongs to Vietnam's Hoang Sa archipelago, as one of the islands under its preservation, upgrading and construction project in 2011.
Nga said all foreign activities on the two archipelagoes without Vietnam's permission are violations of the country's sovereignty.