The government is keeping a close eye on internet use

An official from the Supreme Court of Appeal in Hanoi said the doctor, Pham Hong Son, would serve an additional three years under house arrest.

Mr Pham was sentenced in June after publishing online a feature entitled What is Democracy?, extracted from the US State Department's website.

As was the case in the original trial, diplomats and foreign reporters were not allowed in court.

The Vietnamese Government has been under pressure from international human rights groups to quash the sentence, which they said was intended to silence online political dissent.

A court official said Mr Pham was still guilty of espionage, which theoretically carries a minimum 12 years in jail, but the decision to reduce his sentence was based on "mitigating circumstances", according to the French news agency AFP.

The US embassy in Hanoi said through a spokesman: "We welcome the reduction but he should never have been jailed in the first place for his actions." The embassy called again for Mr Pham's immediate release.

Two dissidents were jailed last year for cyberspace criticism of the communist government.

About a million Vietnamese out of an 80-million-strong population are estimated to have regular access to the web, mainly through internet cafes.

But in 2002, the government tightened regulations on the internet by requiring websites to be licensed and restricted access.