Phan Thanh Hai, who blogged as "Anh Ba Saigon" (Saigon Brother Three), has been held since late Monday after police raided the family home in Ho Chi Minh City, the former Saigon, said his wife Nguyen Thi Lien.

She said the police had seized two desktop computers and a laptop along with numerous documents and articles printed from the Internet.

"Police read us an arrest order for his provisional four-month detention," she told AFP. "They said they have evidence of his writing and publication of false information on his blog."

The blog includes posts and links to writings that touch on sensitive topics in Vietnam. These include a maritime sovereignty dispute with China, a controversial bauxite mining project, a scandal at state-run shipbuilder Vinashin, as well as the cases of prominent dissidents.

Lien said her husband worked in the import-export sector and had never before been arrested.

The US-based Human Rights Watch in May accused Vietnam of mounting a sophisticated and sustained attack on online dissent that included detaining and intimidating anti-government bloggers.

Observers say the government has adopted a more aggressive stance towards politically sensitive Internet sites, although Hai's case appears to be the first in several months.

The government says concerns over free expression in Vietnam are groundless.

Agence France Presse - October 20, 2010