Tens of thousands of Tunisians have marched on the seat of the elected assembly demanding the government resign in one of the largest opposition protests to date.

Saturday marked 40 days since the assassination of opposition politician Mohammed Brahmi, whose killing has plunged the country into a political crisis.

Dozens of opposition members of the assembly withdrew from the body, paralyzing its work of writing the country's new constitution. Weeks of mediation between the government and the opposition by the main labor union have not borne fruit.

The opposition is demanding the Islamist-led government resign for what they say is its failure to ensure security or manage the economy in Tunisia, the birthplace of the Arab Spring.