Thousands of Tunisians protested on Saturday against the new prime minister-designate Ali Larayedh, a hardliner from the main Islamist Ennahda party.
President Moncef Marzouki asked Larayedh to form a government on Friday, in the aftermath of the Feb. 6 assassination of secular opposition politician Chokri Belaid.
Outgoing prime minister Hamadi Jebali resigned on Tuesday because Ennahda rejected his plan for an apolitical technocrat cabinet to prepare for elections.
Larayedh, the new premier-designate, is controversial because opposition secularists accuse the Interior Ministry which he headed of failing to curb Islamist violence.
About 3000 secularists flocked to the capital's main street Habib Bourguiba raising banners hostile to the Ennahda party and Larayedh.
They chanted "Larayedh out" and "The people want to bring down the regime".
Tunisia plunged into political crisis on Feb. 6 when the assassination of secular opposition politician Chokri Belaid ignited the biggest street protests since the overthrow of strongman Zine al-Abidine Ben Ali two years ago.
Larayedh, 57, is viewed as part of Ennahda's hardline wing, which rejects any role for parties linked to the Ben Ali era.
A maritime engineer, Larayedh spent 15 years in jail under Ben Ali.