Tunisian Prime Minister Hamadi Jebali will dissolve the Islamist-led government and form a national unity administration.
In a televised address, the prime minister delivered a speech to the nation and announced the formation of a new government of non-partisan figures and technocrats.
Jabali’s decision, which followed the killing of prominent secular opposition figure Chokri Belaid in front of his home on Wednesday, was a personal one taken in the interests of the country.
He said a gunman wearing a traditional hooded burnouse robe shot Belaid three times at close range as he left his home.
Furious protesters built barricades in central Tunis and clashed with police who fired tear gas to disperse them, and four opposition groups including Belaid’s Popular Front bloc said they were pulling out of the national assembly.
The murder sparked outrage, with violence reminiscent of the uprising that ousted veteran dictator Zine El Abidine Ben Ali just over two years ago, and thousands rallying outside the interior ministry.
In central Tunis a National Guard tank fired tear gas at protesters, who used bins, coffee tables, barbed wire and barriers to build barricades on Habib Bourguiba Avenue.
Security reinforcements arrived after about 20 minutes of skirmishes, and police wearing helmets and armed with clubs charged some 150 protesters, who fled into neighbouring streets.
In central Tunisia protesters torched the Ennahda party office in Mezzouna near Sidi Bouzeid, ransacked another in the mining community of Gafsa and set fire to a party office in the northeastern town of Kef, witnesses said.
In Kasserine, on the border with Algeria, hundreds of people calling for “vengeance” took to the streets, an AFP journalist said.
In Sidi Bouzeid some 2,000 demonstrated peacefully, but around 200 people tried to storm police headquarters. Police fired tear gas to keep them at bay and the army intervened to try to keep the peace.
President Moncef Marzouki denounced the killing of Belaid, an outspoken critic of his government, as an “odious assassination”.
The family of Belaid, who headed the Party of Democratic Patriots which is part of the Popular Front, accused Laraydeh’s Ennahda of being behind the assassination.
The wife of the 48-year-old leftist leader said her husband had received daily death threats and was murdered before her eyes.
“I saw his blood flowing, I saw his little smile. I saw that they want to kill democracy,” Basma Belaid told France’s Europe 1 radio.
Belaid’s brother Abdelmajid squarely accused Ennahda chief for the murder.
“I accuse Rached Ghannouchi of assassinating my brother,” he told AFP.
Ennahda chief Rached Ghannouchi rejected claims Ennahda was behind the “cowardly” murder, and told AFP the killing was a “settling of political scores.”
The killers “want a bloodbath but they won’t succeed,” he said.
The US embassy issued a statement calling the killing an “outrageous and cowardly act.”