Police used batons and tear gas against protesters who tried to break into local government offices in the center - west city of Sidi Bouzid, cradle of the 2011 revolution.
Security forces also fired warning shots to disperse several dozen people demonstrating against what they called the incompetence of the local governor.
The governor is close to the ruling Islamist Ennahda party.
In addition to being where Tunisia ' s Arab Spring began in late 2010, Sidi Bouzid was also the home town of opposition MP Mohamed Brahmi, gunned down in the capital on July 25.
Brahmi ' s was the second political assassination this year, coming after the February murder of Chokri Belaid, also in Tunis. Many Tunisians blame the government for both killings.
At the end of July, hundreds of protesters tried to block civil servants in Sidi Bouzid from going to work, and police used tear gas against stone - throwing demonstrators.
The demonstrators were then also demanding the dismissal of the governor.
An opposition coalition plans another demonstration in Tunis later on Monday, as well as a major night - time protest on Tuesday demanding the government ' s resignation and the dissolution of the National Constituent Assembly.
Tuesday ' s protest will also mark six months since Belaid ' s killing, and is an opposition response to a massive pro - government rally in the capital on Saturday.
As the political crisis festers, with no immediate way out in sight, security forces are pressing their hunt for militants linked to Al - Qaeda holed up in the rugged Mount Chaambi region near the border with Algeria.
Two soldiers killed when their armored vehicle was hit by a blast on Sunday were due to be buried on Monday - - one in Sidi Bouzid and the second in Bizerte in the north, the government said.