The Communist Party newspaper Hanoi Moi said in a front-page article that 50 protesters were taken to police stations Sunday for causing a public disturbance or attacking authorities. It said 11 remained in custody while 39 others were released with a warning.

Demonstrations are rare in Communist Vietnam and are typically quashed quickly by police. However, authorities have allowed anti-China protests to take place for the past 11 weekends, although smaller numbers of people were detained at two of the demonstrations.

Vietnam and China have been at odds since May over territory in the potentially resource-rich South China Sea claimed by both countries. Some observers say tensions have eased since Hanoi sent a special envoy to Beijing in late June and a tentative agreement between China and other Southeast Asian nations was reached at a regional security meeting last month, but anti-China sentiment remains strong among some Vietnamese.

Three weeks ago, an online video clip of a plainclothes security officer stomping on a protester's face outraged the public. Authorities responded by saying that peaceful protests would be allowed, but reversed that decision last week, saying "hostile forces" were leading the demonstrations and provoking public disorder.

About 50 protesters defied the ban on Sunday, waving anti-China banners and shouting slogans. Within minutes, they were rounded up by security forces, shoved into buses and driven away.

The newspaper called the demonstration a "ridiculous farce" organised by "stubborn leaders who abused the fine policy of the state to instigate people to cause public disturbances."

Twenty-five prominent intellectuals and former government officials have signed a petition denouncing the protest ban as unconstitutional.

Agence France Presse - August 23, 2011