The Maritime Safety Administration of China's southern province of Hainan, which oversees the South China Sea, said last month there would be live fire drills around the Paracel Islands, which Vietnam claims, until September 2.
"Vietnam strongly objects this action by China and seriously requests China to respect Vietnam's sovereignty over the Hoang Sa (Paracel) archipelagos," Foreign Ministry spokeswoman Le Thi Thu Hang said in a statement.
"Vietnam once again asserts that (we) will resolutely protect our sovereignty and our legitimate rights and interests in the East Sea (South China Sea) through peaceful measures that are suitable with international laws," the statement said.
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.
Tension between China and neighbouring Vietnam is at its highest in three years over the disputed waters.
Vietnam suspended oil drilling in offshore waters that are also claimed by China in July under pressure from Beijing.
China has appeared uneasy at Vietnam's efforts to rally Southeast Asian countries over the South China Sea as well as at its growing defence relationships with the United States, Japan and India.
(Reporting by Mai Nguyen)