Vietnam on Friday opposed what it called a Chinese announcement of military exercises in the disputed South China Sea, disagreements over which have pushed tension between the neighbors to its highest in three years.
China has appeared uneasy at Vietnam's efforts to rally Southeast Asian countries over the busy waterway as well as at its neighbour's growing defence ties with the United States, Japan and India.
In July, under pressure from Beijing, Vietnam suspended oil drilling in offshore waters that are also claimed by China.
Vietnam was deeply concerned about drills in the region of the Gulf of Tonkin, at the north end of the South China Sea, Foreign Ministry spokeswoman Le Thi Thu Hang said in a statement, but did not make clear what drills were being referred to.
"Vietnam proposes China to cease and refrain from repeating acts that complicate the situation in the East Sea," Hang said, employing Vietnam's name for the South China Sea.
All foreign activities in Vietnamese waters must comply with Vietnamese and international laws, she added.
Vietnam's Foreign Ministry conveyed its position to a Chinese embassy representative on Thursday, the statement added, without saying when China's announcement was made or when any drill might take place.
China's Foreign Ministry did not immediately respond to a request for comment.
Last month, the Maritime Safety Administration of China's southern province of Hainan, which oversees the South China Sea, said military drills would take place south of the province and east of Vietnam from Aug. 29 until Sept. 4.
There would be live fire drills around the Paracel Islands, which Vietnam claims, until Sunday, it added.
China claims nearly all the South China Sea, through which an estimated $3 trillion in international trade passes each year. Brunei, Malaysia, the Philippines and Taiwan also have claims. (Reporting by Mai Nguyen; Additional reporting by Ben Blanchard in Beijing; Editing by Alison Williams and Clarence Fernandez)