Authorities in Hanoi Thursday ordered a ban on all unauthorized demonstrations citing political and security concerns, the Vietnam News Agency reported.
The Hanoi People's Committee asked related agencies to carry out campaigns to inform the public about the order and encourage them to comply.
If anyone deliberately refuses to follow the order, all necessary measures will be taken to maintain public security, the news source quoted authorities as saying.
The municipal administration said that since June many demonstrations, marches and gatherings protesting China's violation of Vietnam's sovereignty have been taking place every Sunday.
While the early ones were patriotic in nature, some of the recent activities have been provoked by anti-government forces, disturbing public security, it said.
The forces aimed to divide the people of Vietnam, undermine diplomatic relations between Vietnam and China, and cause political disorders, the committee said.
It also said that the "spontaneous" gatherings, marchings and demonstrations had caused "bad influences" on security and contradicted the capital's reputation and image as "the city of peace," they said.
On May 26 a Chinese marine surveillance vessel cut the exploration cables of a Vietnamese vessel which was conducting seismic surveys in the nation's territorial waters.
Two weeks later, Viking II, a Norwegian ship contracted by PetroVietnam Technical Services Corporation and the French-owned CGG Veritas Joint-venture, was also harassed by Chinese ships.
Both incidents happened well inside Vietnam's 200 nautical mile (370 kilometers) Exclusive Economic Zone, sparking an outcry among the public, both in Vietnam and abroad, and continuous demonstrations were held in the capital over the past weeks.