Vietnam’s navy has been conducting live-fire artillery drills following increased tensions with China.
The exercises are taking place off 40 kilometres from the country’s central coast, near an unoccupied island.
Tensions have arisen over who has control of parts of the South China Sea.
The waters are in dispute since an alleged invasion of Vietnamese territory by Chinese ships two days ago.
China has strongly criticized the drills through local government media, calling it a defiance against Beijing.
Vietnamese government officials have referred to the drills as routine training.
Both nations are known to be touchy about possession of areas in the South China Sea, known to be rich in oil and gas reserves.
Many other countries in the area, including Indonesia, Taiwan, Brunei, Malaysia and the Philippines also have competing claims over the sea area.