Truong Duy Nhat, 49, faces up to seven years in jail on accusations of "abusing democratic freedoms to infringe on the interests of the state", state-run media has reported.

As online dissent has grown in Vietnam, government agencies have this year convicted more than 38 activists and bloggers of anti-state activity.

In April Mr Nhat, a former journalist at state-run newspapers, called on Vietnam's top leaders to resign to save the nation from its economic and political woes.

He also conducted an online opinion poll just weeks before the National Assembly's first-ever confidence vote on top officials, scheduled for early June.

Mr Nhat's blog has been closed since he was arrested in his home city of Danang on Monday and taken to Hanoi for questioning.

Vietnam bans private media: all newspapers and television stations are run by the state. Bloggers and activists are regularly subjected to arrest and detention, rights groups say.

In February journalist Nguyen Dac Kien was fired from his state-run newspaper after criticising the head of the ruling communist party on his blog.