Witnesses in Sousse say security forces fired tear gas to disperse hundreds of angry protesters blocking roads.
Violent protests broke out in several Tunisian cities, including the capital Tunis and the coastal city of Sousse, as anger mounts over economic hardship.
The demonstrations on Saturday night come as Tunisia marks the tenth anniversary of the revolution that toppled late president Zine El Abidine Ben Ali and sparked the Arab Spring uprisings.
Demonstrations in Siliana and other cities began on Friday after a video posted on social media showed a police officer shouting and pushing a shepherd whose sheep entered the local government headquarters.
Dozens of protesters built barricades and set fire to objects to block the streets of the city, 130km (80 miles) from Tunis.
The protests pose a challenge for the government of Hicham Mechichi, who earlier reshuffled the cabinet with new ministers including the ministries of interior, justice and energy.
Witnesses in Sousse said security forces fired tear gas to disperse hundreds of angry protesters who were blocking roads and burning tyres.
Security sources said young men in Sousse broke into shops. Clashes took place in the city of Kalaa Kebira near Sousse.
A decade after the revolution against widespread unemployment, poverty, corruption and injustice, Tunisia made smooth progress towards democracy, but its economic situation worsened with poor public services and the country on the verge of bankruptcy.
Violent protests also took place in several parts of the capital, including Ettadamen, Mallassin and Fouchana and Sijoumi. There were also night protests and riots in Kef and Bizerte.
No festive celebrations were held marking the revolution in Tunisia.
The North African nation’s government imposed a four-day lockdown starting on Thursday to contain the coronavirus, banning demonstrations expected for that day.
Some citizens questioned the timing of the four-day lockdown.
The revolution was unwittingly sparked by a desperate act of a 26-year-old fruit seller, Mohammed Bouazizi, who set himself ablaze on December 17, 2010, to protest police humiliation in Sidi Bouzid, a town in Tunisia’s neglected interior of the nation.
Bouazizi’s death unleashed simmering discontent and mass demonstrations against poverty, joblessness and repression.