Vietnam demands that China immediately halt all its activities violating the country's sovereignty at the Hoang Sa (Paracel) and Truong Sa (Spratly) archipelagos, the foreign ministry's spokesperson has said.

Addressing a regular press conference of the Ministry of Foreign Affairs, spokesman Luong Thanh Nghi condemned China's recent activities and projects, including its officials' visits to the islands, saying that all activities happening there without Vietnam's consent were violation of its sovereignty.

They were also against the ground rules on resolving sea issues that the two countries signed last year, the Declaration on the Conduct of Parties in the South China Sea, and commitments to maintaining peace at sea, Nghi said.

According to a report on the government's website, Chinese media recently reported that Transport Minister Li Shenglin visited Hoang Sa to examine a patrol ship, while the head of its sports department visited Hoang Sa's Phu Lam Island for checking the progress of sporting activities there.

Moreover, the Nanhai institute for environmental research and oceanic projects is reported to have started a research on changes happening in some islands of the Hoang Sa archipelago.

China also plans to build fishing establishments and a wharf at the islands, the website reported.