Vietnam's communist rulers have ordered a crackdown on anti-government blogs, two of which immediately pledged fresh defiance Thursday against the one-party state.

The government does not allow freedom of expression or the media, but has been struggling against dissent being propagated over the Internet. The Communist Party fears that public criticism or even honest discussion about its failings could lead to social instability and — ultimately — loss of power. It labels democracy and free speech activists as "terrorists."

A government statement late Wednesday named three blog sites it accused of "publishing distorted and fabricated articles" against the leadership.

"This is a wicked plot of the hostile forces," it said, adding that Vietnamese state employees were forbidden from visiting the sites.

The statement said Prime Minister Nguyen Tan Dung had ordered police to investigate the sites and bring offenders to justice.

Reaction was swift from two of the named sites, which feature postings criticizing government corruption and alleged human rights abuses by mostly anonymous contributors.

Danlambao, or "the People's Journalism Blog," said it would keep publishing.

"Danlambao and its companions are prepared to be repressed and imprisoned rather than leading the life of a dumb dog that dares not to bark, subservient to those who abuse their power," it said in a blog posting.

Quanlambao, or "Official Journalism," also responded, saying Dung's move was aimed at creating the legal basis to make arrests in accordance with a "planned scenario."

International watchdog Reporters Without Borders says there are currently at least five journalists and 19 bloggers being held on various charges in Vietnam, part of a gathering government effort to stifle criticism of the regime.