Hundreds of opposition activists protested in central Tunis on Wednesday demanding the resignation of Tunisia's Islamist-led government, ahead of a national dialogue aimed at ending months of political deadlock.
The protesters gathered on central Habib Bourguiba Avenue, waving Tunisian flags and shouting slogans such as: "The people want the fall of the regime", "Get out" and "Government of traitors, resign!"
The demonstration took place amid a heavy security presence, with armoured vehicles and anti-riot police deployed along the central Tunis boulevard, which was the epicentre of the January 2011 revolution that ousted former dictator Zine El Abidine Ben Ali.
A separate pro-government protest called for 0800 GMT by the League for the Protection of the Revolution had failed to materialise by midday.
Wednesday's demonstration came just hours before the start of a planned national dialogue between the ruling Islamist party Ennahda and the opposition.
Mediators hope the talks will bring an end to the political paralysis gripping the country since the July killing of opposition MP Mohamed Brahmi and mark a crucial step in the country's democratic transition.
Tunisian officials say they expect Islamist Prime Minister Ali Larayedh to announce his commitment to resign ahead of the talks.
According to a political roadmap drawn up by mediators, the national dialogue will lead within three weeks to the formation of a new caretaker cabinet of technocrats.
Negotiators will also have one month to adopt a new constitution, electoral laws and a timetable for fresh elections, key milestones in the democratic transition which has effectively been blocked by wrangling between the Islamists, their coalition allies and the opposition.
A senior member of Ennahda charged on Tuesday that the opposition was preparing to "destroy" the negotiations between the two sides by staging anti-government protests.