A Tunisian opposition party leader who criticised the Islamist-led government and violence by radical Muslims was shot dead outside his home today, officials said.
Chokri Belaid was targeted as he left his house in the capital, Tunis, the Unified Democratic Nationalist Party said.
More than 1,000 Tunisians protested outside the Interior Ministry against the killing.
Chanting for the fall of the Islamist-led government, demonstrators shouted "Shame, shame Shokri died", "Where is the government?", and "The government should fall".
Security forces cordoned off the area.
Witnesses said Mr Belaid was taken to a nearby clinic and died.
He was critical of Tunisia's leadership, especially the moderate Islamist party Ennahda which dominates the government.
Government spokesman Samir Dilou called it an "odious crime".
The reason for the killing is unclear. It comes as Tunisia struggles with social and religious tensions after its long-time dictator, Zine El Abidine Ben Ali, was overthrown in an uprising two years ago that set off revolts across the Arab world.