Tunisia was plunged into a fresh political crisis after opposition politician Mohamed Brahmi was gunned down Thursday outside his home in Tunis in the second such assassination this year, dpa reported.
Brahmi, 58, was the leader of the small nationalist Movement of the People party. He was killed in the El Ghazala suburb of northern Tunis as the country celebrated Republic Day, the Interior Ministry said.
"He left the house and got into his car. ... As soon as he got into the car he was riddled with bullets," his wife told Tunisia's Business News website.
A daughter told Mosaique FM that Brahmi had rushed to the car after receiving a phone call. Witnesses told local media they saw two people flee by scooter.
The powerful UGTT labour confederation called for a general strike Friday to coincide with Brahmi's burial.
Thousands of people took to the streets Thursday to protest the killing, which comes six months after the assassination of Chokri Belaid, a leader of the leftist Popular Front coalition that Brahmi's party had recently joined.
Demonstrators shouting slogans condemning the ruling Islamist party Ennahda and calling for the fall of the elected "regime" gathered outside the hospital where his body was taken. Many waved Tunisian flags.
Several hundred protesters rallied outside the Interior Ministry.
In the central town of Sidi Bouzid, demonstrators set fire to the local governorate building. Protesters torched Ennahda offices in the region, which is the birthplace of Brahmi and of Tunisia's 2011 revolution against strongman Zine El Abidine Ben Ali - the first of the so-called Arab Spring uprisings.
The Popular Front demanded the dissolution of the Constituent Assembly elected in Tunisia's first democratic polls in October 2011 and called for the creation of a "government of national salvation."
Brahmi was a member of the assembly, which has seen intense debate recently over a new draft constitution. He had been critical of Ennahda, accusing it of emasculating state institutions, but was not a high-profile politician.
Beji Caid Essebsi, leader of the biggest opposition party, Nidaa Tounes, said Brahmi's death made all outspoken government critics potential targets.
The latest killing bore the hallmarks of the attack on Belaid, who was gunned down on February 6 outside his home by a suspected radical Islamist, who is still being sought by police. That attacker likewise escaped on a scooter.
The opposition has accused Ennahda of bearing political responsibility for both killings - allegations it rejects. The party, which has been weakened by the ouster of the allied Muslim Brotherhood in nearby Egypt, strenuously condemned the Brahmi attack.
Ennahda party leader Rached Ghannouchi said the "cowardly and despicable crime" was "an attempt to prevent Tunisians from achieving success in a region shaken by divisions and instability." Dissolving the assembly would solve nothing, especially given that elections were planned soon, he said.
Prime Minister Ali Larayedh condemned the "hateful crime against Mr Brahmi and the stability of the country." President Moncef Marzouki urged Tunisians to avoid being baited by violence.
The United States called the assassination a "cowardly act."
US State Department spokeswoman Marie Harf called for a "transparent and professional investigation" and for Tunisians to remain calm, saying that violence is "not an appropriate response to this murder."
UN High Commissioner for Human Rights Navi Pillay, German Foreign Minister Guido Westerwelle and French President Francois Hollande, who had recently praised Tunisia as a model for the Arab world, condemned the attack.