Human rights groups have complained to the Tunisian president

About 30 policemen manhandled Mr Hammami and his comrades from the court in Tunis on Saturday as their appeal against previously imposed prison sentences was being heard.

Mr Hammami's young daughter was injured as she tried to hold on to him.

Lawyers described the police action as an abduction and have declared a strike in protest at the police action, to begin next Thursday.

A group of 11 European-based human rights groups has sent a letter to the Tunisian President, Zine El Abidine Ben Ali, expressing their outrage at the proceedings.

'Media targeted'

The letter, from groups including Reporters sans Frontieres; the Swiss Rights League and the Bar Council of England and Wales Human Rights Committee, said the court hearing was marked by grave violations of the rule of law and violence against members of the press.

It said security in the court should have been guaranteed by the judge alone, without the intervention of police.

The groups also condemned action taken against the media and demanded that material taken from three French television stations be returned.

Picture of Hamma Hammami, courtesy of Amnesty International

In 1999, three of the senior party figures were sentenced in their absence to more than nine years in prison for dissident activity.

The fourth had been given a shorter sentence - again in his absence - in 1997.

All four were being hunted by police.

They say that their trials were unfair and that they surrendered to the court so they could appeal against their sentences.

The four said they believed pro-democracy opposition forces and human rights groups had grown strong enough to pressure the authorities for a fair trial.

Tunisian law allows for people sentenced in absentia to have a retrial when they give themselves up to a court.

But, as international observers looked on, policemen poured into the courtroom and the four accused were taken away.

They were later brought back - in handcuffs and with their shirts torn - after their lawyers had left.

Sentences upheld

Police then dragged them away again after they shouted that they had been beaten, and one of them tried to show marks on his body.

According to reports, Hamma Hammami and Samir Taamallah had their original sentences of nine years and three months confirmed.

Abdejabbar Madouri had the same sentence confirmed plus another two years for contempt of court when he questioned the independence of the judiciary at the hearing.

Ammar Amroussia had his sentence of two years and three months confirmed.

Campaign to continue

Speaking before his court appearance, Mr Hammami told French radio that he and his colleagues were not extremists or outlaws, but had "refused to submit to dictatorship... and repressive laws".

He said that, even if imprisoned "we will continue the struggle from the darkest corners of our cells".

Human rights groups accuse the Tunisian authorities of widespread violations and of using the courts to silence political opponents.

Amnesty International press officer George Ngwa told BBC News Online on Saturday that his organisation wanted to see Mr Hammami have a retrial that was free and fair, and "that meets international standards".