Vietnamese police have broken up anti-China protests in two cities and detained 20 people in the first such demonstrations since tensions between the communist neighbours flared anew over rival claims to the oil and gas-rich South China Sea.
Hundreds of protesters, some waving banners and chanting "Down with China's aggression!", were intercepted by security forces as they tried to approach the Chinese embassy in the capital, Hanoi, on Sunday.
Activists at the scene said that the 20 demonstrators were rounded up into a bus after the half-hour rally, the fifth such display of public discontent in Hanoi this year against Beijing's perceived aggression in the sea.
Security forces also broke up a similar anti-China protest in the southern economic hub of Ho Chi Minh City.
Protesters shouted "Down with China" and carried banners bearing the slogan "China's military expansion threatens world peace and security."
Using loudspeakers, authorities urged them to disperse and tried to reassure them that "the Communist Party and government are resolutely determined to defend our country's sovereignty and territory through peaceful means based on international law."
Vietnam and China have long sparred over who owns the South China Sea, which is also claimed in whole or part by Taiwan, Brunei, Malaysia, and the Philippines.
Vietnam last week alleged that Chinese shipping vessels sabotaged one of its seismic survey vessels in the South China Sea.
This week the government warned Beijing not to do that again and presented a list of its violations in the disputed sea.
China responded by denying the allegations and demanding that Vietnam stop its navy harassing Chinese boats.
China recently issued new passports containing a map showing the sea as belonging to it, causing anger in Hanoi and other regional states.
The South China Sea is strategically significant, home to some of the world's most important shipping lanes and believed to be rich in resources.