A prominent Tunisian human rights activist has been arrested in order to enforce a 20-year prison sentence, following a mass sentencing of government critics in a controversial trial.

Chaima Issa, an activist who took part in the 2011 protests that ousted longtime ruler Zine El Abidine Ben Ali, was taken by police on Saturday afternoon at a protest in the capital, lawyers said.

On Friday, dozens of opposition figures were sentenced on appeal to prison terms of up to 45 years on charges of "conspiracy against state security" and "belonging to a terrorist group".