More than 700 protesters gathered in Kasbah square in the centre of the Tunisian capital but were quickly dispersed by hundreds of police officers in riot gear.
Protesters shouted “We are not afraid” as police pushed them out of the square, where Prime Minister Beji Caid Sebsi has his office.
Protests also took place in Sidi Bouzid, the central Tunisian town where a vegetable seller set himself on fire last December, setting in train protests that brought to an end the 23-year rule of President Zine al-Abidine Ben Ali.
The demonstrators, angered by what they see as the interim government’s failure to live up to the promise of Tunisia’s “Jasmine Revolution”, chanted: “We want a new revolution.
Mehdi Alharchana, one of the protesters in Sidi Bouzid, told Reuters: “People are angry. Nothing has changed and frustration is haunting everyone.”
Demonstrations and strikes have rumbled through Tunisia in recent weeks and months, echoing popular discontent with slow progress with reforms since the fall of Ben Ali.
On Wednesday, soldiers fired in the air to break up clashes between hundreds of young people in the southern town of Gafsa.
Since Ben Ali fled to Saudi Arabia six months ago — an event that sparked the upheavals now shaking much of the Arab world — Tunisia is undergoing an uncertain political transformation and the economy is in grave difficulties.
Elections to a body that will be charged with drawing up a new constitution have been put back to October.
The economy has stagnated in the first half of the year, which has seen a 50 percent drop in vital tourist revenues.