Fifty Tunisian policeman were hurt in clashes with protesters in the marginalised town of Siliana where a general strike degenerated into violence, the interior ministry said on Thursday.
The violence broke out on Wednesday as the town observed a strike to mark the first anniversary of riots that left more than 300 people injured, and as strikes were held in two other regions amid rising social discontent and political deadlock.
"Fifty agents were injured to varying degrees in the troubles, some of them suffering fractures," the ministry said, adding that two of them were badly wounded.
Police vehicles and public and private buildings were damaged during the unrest.
"(The police) managed to control the situation only using tear gas in extreme cases," the ministry said, while insisting that all those who take part in or incited the violence would be prosecuted.
Earlier, a medical source said the hospital in Siliana treated 32 people injured in Wednesday's clashes, nearly all of them Tunisian police, adding that they had all since had been discharged.
Violence also took place in the poor central town of Gafsa, where protesters torched an office of the ruling Islamist party Ennahda.
Wednesday's clashes erupted when hundreds of demonstrators marked the first anniversary of violence that left more than 300 people injured, when anti-government marches exploded into days of running clashes between police and protesters.
The clashes lasted late into the night, with some of 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, when the extent of the violence became apparent with trees charred, signs torn down and debris littering its streets.
The regions of Gafsa and Gabes also 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 autocrat Zine El Abidine Ben Ali nearly three years ago and sparked revolutions across the region.