Vietnam has protested Chinese military drills in a group of islands that both countries claim, calling them a violation of its sovereignty.
Vietnam's Foreign Ministry said in a statement posted late Thursday on its website that China's navy conducted counter-piracy drills in the Spratly island archipelago in the South China Sea a week earlier.
The ministry says its representatives met with Chinese embassy officials on Wednesday to lodge a protest.
Vietnam's ministry says China's actions violated Vietnamese sovereignty. It says it asked China to refrain from activities that would further complicate the competing claims to the islands.
The Spratlys are also claimed by other Asian nations and believed to be sitting atop vast oil and gas reserves.