Police fired tear gas Friday on stone-throwing youths in Tunisia's capital after a demonstration by hundreds of Islamists protesting the country's secular laws.
The violence at the end of a day of peaceful, small protests disrupted a period of relative calm in the North African country, where an uprising ousted the longtime president in January and prompted revolts around the Arab world.
It was unclear whether anyone was injured or arrested in the clash.
Protesters held two demonstrations in Tunis on Friday, one by a group demanding more economic freedoms and another by young Islamists shouting "God is great" and other religious slogans.
Their demonstration came as the Interior Ministry announced Friday that women are no longer required to take off headscarves for official state ID cards. The Islamist protesters want the government to remove restrictions on the headscarf in public buildings and other measures.
A strong secular flavor pervades this former French colony, partly because ousted President Zine El Abidine Ben Ali and his predecessor, Habib Bourguiba, kept Islamists in check. Even though 98 percent of the population are Muslims, only a minority of women wear Islamic headscarves, and Friday, the Muslim day of rest and special prayer, is part of the Tunisian work week.
Police showed up in force Friday to ring the historic Casbah to try to prevent violence at the planned protests. The Casbah saw tensions during protests earlier this year, in which scores of people were killed when police under Ben Ali's hard-line regime fired on protesters.
Friday's demonstrations were mostly peaceful, with a few hundred people, including Islamists in white prayer caps.
In the evening groups of youth marched near the Casbah and clashed with police, who responded with volleys of tear gas.
Karin Laub in Tunis contributed to this report.