PRAGUE (AFP) - Academics have urged Czech President Vaclav Klaus to pardon the artists who pirated a public television broadcast and superimposed an image of a nuclear mushroom cloud over mountain scenery.

The "Ztohoven" group won international fame and a national art prize for the images aired on the early morning "Panorama" programme, which regularly shows webcam pictures of beauty spots with weather details, on June 17.

The seven-strong group is due to appear in court on March 25 in the north-eastern town of Trutnov.

They face sentences of up to three years for "scaremongering" for a stunt which was aimed at "invading media and television territory intruding and impeaching its truth as well as its credibility", according to their website.

Academics at Prague's prestigious Charles University have launched a petition calling for Klaus to exercise his powers of clemency to stop the trial or pardon the artists if they are found guilty.

The academics argue that the court case is ridiculous and a waste of money. "The image introduced onto the broadcast was so absurd that it is impossible to regard it as scaremongering," they said in a statement.

The petition had gathered 3,500 signatures within its first three days, one of the protest organisers, teacher Denisa Kera, told AFP.

The piece of performance art was intended to highlight the difference between the real and media created worlds and to sharpen Czech's critical capacities, they added, echoing the artists own justification.

"The artists have become world famous and have promoted Czech culture and now we are punishing them," added 33-year-old Kera.