The attorney-general's office said there was insufficient evidence to press charges against Clive Wilson who was questioned over the weekend after being arrested on Friday.

Police said they were still investigating the matter involving The Standard newspaper and might charge Mr Wilson at a later date.

The arrest of Mr Wilson came after the alleged torture of the newspaper's editor Mark Chavunduka and Ray Choto, the chief writer.

Released: Ray Choto and Mark Chavunduka

The pair alleged that they had been subjected to electric shocks, beatings and degrading treatment.

Mr Chavunduka was said to have been subjected to partial drowning as his interrogators allegedly attempted to force him to reveal the source for a story that army officers had been arrested for attempting a coup.

A BBC correspondent witnessed their hearing in court and described their appearance as shaken and dizzy.

Defence Minister, Moven Mahachi denied the torture allegations.

Mr Wilson, who was arrested for the same offence as the two journalists, publishing false information, was reported as saying that the press "would not be cowed".

Investigation calls

Human rights campaigners have called for an investigation into the arrests and torture.

Since his release, Mr Choto has alleged that his house is under surveillance and that both men have been warned not to talk.

Also last week, six other journalists were assaulted by a security agent and a union leader left unconscious, having been beaten with an iron bar. One of his assailants was allegedly a police officer.

The Zimbabwe union of journalists has called on the international community to impose sanctions and withhold aid in protest.

The International Press Institute, an umbrella body which campaigns for world media freedom, has described journalists in Zimbabwe as operating at times "in a climate of fear".

Last year campaigners opposed the Public Order and Security Bill which, they said, posed a significant threat to freedom of expression, speech and association.