Truong Duy Nhat, 49, was arrested yesterday at his home in coastal Danang city and escorted to Vietnam's capital Hanoi for questioning, the state-run Tuoi Tre newspaper said.
He stands accused of "abusing democratic freedoms to infringe on the interests of the state", a charge that could result in a maximum seven years in jail, the report said.
Nhat, who had worked for Vietnam's official press but quit in 2011, writes the popular blog "A Different Viewpoint".
It has not been possible to access his blog -- which frequently dealt with highly sensitive political issues -- since his arrest.
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In a late April post, Nhat called for Vietnam's top leaders to resign, saying "it's time for a new party general secretary and prime minister" to save the nation from its economic and political woes.
Vietnam bans private media, with all newspapers and television channels state-run. Lawyers, bloggers and activists are regularly subject to arbitrary arrest and detention, according to rights groups.
So far in 2013, at least 38 activists have been convicted of anti-state activity under what rights groups say are vaguely defined articles of the penal code.