Dozens of protesters were arrested Sunday when around 150 people demonstrated against China in the capital of Vietnam.
Witnesses said between 30 and 50 people were detained when the crowd started to march around the central Hoan Kiem lake.
Protesters were wearing T-shirts and carried placards calling for an end to Chinese aggression in the South China Sea.
“We are protecting our country so we’re not afraid of anything,” Nguyen Anh Dung said shortly before he was taken away by police.
The Ministry of Foreign Affairs last week accused Chinese boats of colliding with Vietnamese fishing vessels near the disputed Paracel Islands.
China called the accusations “totally untrue,” saying a Vietnamese fishing boat had entered Chinese waters illegally.
China claims most of the 3.5 million square kilometres of the South China Sea. Vietnam, the Philippines, Malaysia, Brunei and Taiwan also have overlapping claims to the sea, which straddles key shipping lanes and is believed to be rich in resources.