Thirty-two people were injured, nearly all of them Tunisian police, when a strike degenerated into violence in the town of Siliana, southwest of the capital, a hospital source said on Thursday.
The violence erupted on Wednesday when protesters clashed with police in Siliana and Gafsa, another marginalised town where they torched an office of the ruling Islamist party Ennahda.
Of those injured in Siliana, 30 were members of the police force who suffered mainly slight injuries to their heads and faces, said the hospital source, adding the two others were youths with leg wounds.
All of them had since been discharged from hospital.
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Wednesday's clashes erupted when dozens of demonstrators marked the first anniversary of violence that left more than 300 people injured during anti-government demonstrations.
The clashes lasted late into the night, with the protesters hurling rocks at police and placing burning tyres in the town centre as the police tried to disperse them by driving into the crowd and firing tear gas.
Calm had returned to Siliana on Thursday morning, when the extent of the violence became apparent with trees charred, signs torn down and debris littering its streets.
The regions of Siliana, Gafsa and Gabes ground to a halt on Wednesday as strikes were observed to protest against poverty and lack of development.
Those were driving factors behind the popular uprising that toppled veteran strongman Zine El Abidine Ben Ali nearly three years ago and sparked revolutions across the region.