Recent activity by China's strategic bombers in the South China Sea's Paracel Islands seriously violated Vietnam's sovereignty over the disputed territory, Vietnam's foreign ministry said on Monday.
China's air force said bombers such as the H-6K had landed and taken off from islands and reefs in the South China Sea last week as part of training exercises.
The flights "increase tensions, cause regional instabilities and are not good for maintaining a peaceful, stable and cooperative environment in the East Sea," foreign ministry spokeswoman Le Thi Thu Hang said in a statement, using the Vietnamese name for the South China Sea.