Around 100 Vietnamese protested outside the Chinese embassy in Hanoi for the second consecutive Sunday, demanding that China stay out of waters claimed by Vietnam.
The protesters were surrounded by riot police and security personnel and dispersed peacefully after about half an hour. The demonstrators were also allowed to march through the streets of the Vietnamese capital. Another protest took place in Ho Chi Minh City in the south of the country.
The demonstrations took place ahead of live-fire naval exercises that the Vietnamese Foreign Ministry said will take place Monday off the central coast.
China and Vietnam are at odds over two incidents in which China interfered with Vietnamese vessels conducting oil exploration in disputed waters.
China, Vietnam, the Philippines, Malaysia, Brunei and Taiwan all claim South China Sea territories, which are thought to hold large oil and gas reserves.