Police have fired tear gas and shot into the air to break up demonstrators protesting against Tunisia's Islamist-led government.
Protests had been taking place in the southern town of Sidi Bouzid, the birthplace of the country's 2011 revolution.
Witnesses told Reuters that police opened fire after protesters tried to prevent the governor from entering the town hall.
The secular opposition, which is trying to topple the government, has called for civil disobedience and the occupation of government offices.
Tunisia is grappling with large pro- and anti-government protests, as well as a growing security threat.
Islamist militants have stepped up attacks in the past two weeks and Tunisian forces launched heavy air and artillery strikes on militant hideouts near the Algerian border.
The assassination of leftist figure Mohamed Brahmi on 25 July sparked the worst political crisis in Tunisia since protests toppled autocratic leader Zine El Abidine Ben Ali in 2011.
Mr Brahmi was the second opposition figure to be killed in six months.
The opposition demands the dissolution of the government and the Constituent Assembly, which is just weeks away from finishing a draft constitution and a new electoral law.
Ennahda, the Islamist party that is governing in coalition with other forces, says it will negotiate on changing the government.
However, it has refused to remove the prime minister or dissolve the assembly, which it has called its "red lines".
