The European Union's foreign affairs chief is demanding that Vietnam release a French-Vietnamese academic and blogger who was sentenced this week on subversion charges.

Catherine Ashton issued a statement Thursday saying she is “seriously concerned” about the three-year prison term handed Wednesday to Pham Minh Hoang. The 56-year-old math professor was convicted of “carrying out activities aimed at overthrowing the people's administration.”

Ashton said Hoang's imprisonment is not “consistent with the fundamental right of all persons” to freely and peacefully express their opinions.

Hoang's conviction has drawn similar statements from the French Foreign Ministry and the U.S. State Department, as well as human rights groups Amnesty International and Reporters Without Borders.

He will receive credit for the one year he has already spent in detention awaiting trial, but faces three more years of house arrest following the end of his prison term.

Hoang's wife says she believed her husband was targeted because of his opposition to a Chinese-run bauxite mine in the Central Highlands. Environmental activists say the mine has caused environmental degradation in the area.