The verdict in southern Vietnam meant Dinh Nhat Uy was released from detention.
The charge sheet against Uy was the first to mention Facebook by name. The social network is frequently used by dissidents to spread news, video and photos supporting their campaign for multiparty democracy, alarming Communist rulers who used to have a monopoly on information.
In a measure of the difficulties facing the government, news of the verdict spread quickly across Facebook, with many people using the opportunity to post critical commentary. Activists seeking to get close to the heavily guarded courtroom in Long An province reported several people were detained, according to accounts on Facebook.
Uy's lawyer Ha Huy Son said he was convicted of "abusing democratic freedoms" by posting criticism of the government and state-owned companies. The crime carried a maximum sentence of three years.
Vietnamese courts have convicted and imprisoned at least 46 bloggers or democracy activists this year on national securing charges, more than twice the number in 2012. Foreign governments, led by the United States, and international rights groups have criticized the crackdown and called for the activists' release.
A law that took effect in September banning the sharing of news and content critical of the government on social media networks. No one has yet been charged under that law, which given the volume of content carried on Facebook would appear to be hard to enforce
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