Police clashed with thousands of anti-government protesters who tried to storm Habib Bourguiba Avenue in Tunis on Monday, defying a ban on demonstrations in the area - a focal point of the revolt that ousted Zine al-Abidine Ben Ali over a year ago.
About 2,000 protesters marching from the nearby headquarters of the main labour union, which has been at the forefront of opposition to the Islamist-led government, were met by riot police at the interior ministry on Bourguiba Avenue.
The moderate Islamist Ennahda party, which won elections last year, is under pressure from secular parties and the labour union not to give religion too prominent a place in public life - and from Salafist parties wanting the opposite.
Protesters on Monday also likened Ennahda to the Trabelsi family of Ben Ali's wife Leila, widely blamed by Tunisians for the rampant corruption of the final years of his rule. The people are sick of the new Trabelsis, protesters chanted.
Police beat back protesters with batons and fired tear gas to break up the crowd, chasing stone-throwing demonstrators down side streets in scenes reminiscent of the tactics used during Ben Ali's 23 years as president, when Tunisia was a police state and freedoms severely restricted.
The people want the fall of the regime, protesters chanted, echoing the demand that was coined in Tunisia during the 2011 revolution and sparked the Arab Spring uprisings.
No fear, no terror, the street belongs to the people, the crowds chanted as they confronted police.
Hundreds more protesters were heading towards the central street from other areas after an online call to march on Bourguiba Avenue on the April 9 Martyrs' Day holiday, marking the suppression of pro-independence demonstrators by French colonial troops in 1938.
Tunisia has changed enormously since the revolution, with a democratic system now in place and ordinary people able to speak and demonstrate freely for the first time in memory.
The interior ministry decided to ban rallies on Habib Bourguiba Avenue in late March after local hotels, restaurants and other businesses complained that repeated protests and counter-protests were snarling traffic and disrupting business.
Tunisia's revolution ousted Ben Ali in January 2011. In October, in the country's first free elections Ennahda won 40 percent of seats in the constituent assembly that will draft the new constitution.
From the outset, Ennahda has faced strong opposition from secular parties and Tunisia's powerful labour union, who fear it will impose conservative religious values on a country long known for its liberal and secular outlook.
Ennahda has promised not to ban alcohol or enforce the veil but has also faced pressure from conservative Salafi Islamists pushing for a greater role for religion in public life.
The party, which leads the government in coalition with two secular groups, has tried to steer a middle course but the clashes with protesters are likely to cause controversy.
(Writing by Lin Noueihed; Editing by Tim Pearce)