Tens of thousands of Tunisians turned out for the funeral of assassinated secular politician Mohammed Brahmi on Saturday, and called for the Islamist-led government to be toppled.
Meanwhile, a man was killed in violent overnight protests and a car bomb exploded in the Tunisian capital on Saturday, shortly before the funeral of an assassinated leftist politician.
The death of secular opposition figure Brahmi, gunned down outside his Tunis home on Thursday, has heightened tensions in the North African country and turned up the pressure on its Islamist rulers.
Witnesses said one man was killed early on Saturday in an anti-government protest in the southern city of Gafsa. Violence also broke out in several other cities.
A bomb in a police car exploded at dawn on the outskirts of Tunis but caused no casualties, a spokesman at the Interior Ministry said.
Military helicopters hovered above Brahmi's funeral procession on Saturday morning, and hundreds of troops and police lined the route of a procession attended by Brahmi's family and several prominent politicians.
The funeral procession is to walk down the main street of the capital, near the Interior Ministry. Hundreds of police were deployed in anticipation of violence.
Tunisian police fired tear gas in front of the parliament building, a Reuters reporter said, to disperse secular protesters demanding the dissolution of the assembly and Islamists defending the legitimacy of their rule.
Brahmi's family has accused the main Islamist al-Nahda party of being behind the killing. Its leader, Rached Ghannouchi, has denounced the assassination as an attack on democracy.
Divisions between Islamists and their secular opponents have deepened since President Zine al-Abidine Ben Ali was toppled in 2011.
Late on Friday, 42 opposition members announced their resignation from the 217-seat Constituent Assembly to protest against the killing of Brahmi, a member of the Arab nationalist al-Tayar al-Shaabi party.
Khamis Kssila of the Nida Touns party said the departing members would begin a sit-in to demand the dissolution of the assembly and formation of a national salvation government – ideas rejected by Prime Minister Ali Larayedh.
The assembly, controlled by Islamists, is in charge of drafting a new constitution for the nation of 11 million people.
Several thousand Islamists took to the streets of Tunis on Friday to defend the government from popular demands that it resign over the assassination.
Interior Minister Lotfi Ben Jeddou drew a direct link between the latest killing and the assassination of the Democratic Patriots’ Movement leader, Chokri Belaid, on February 6, which also stoked violent protests.
Aiming suspicion at a hardline Islamist, the minister said the same gun had been used in Thursday's killing as in the Belaid assassination.
"The same 9mm automatic weapon that killed Belaid also killed Brahmi," he told a news conference, naming the main suspect as Salafi Boubacar Hakim, already being sought on suspicion of smuggling weapons from Libya.
Authorities have identified 14 Salafis suspected of involvement in Belaid's assassination, and most were believed to be members of the local hardline Islamist group Ansar al-Sharia, he said.
Tunisia's political transition since the revolt that toppled Ben Ali has been relatively peaceful, with the moderate Islamist al-Nahda party sharing power with smaller secular parties.
But the government has struggled to revive the economy and has come under fire from secularists who accuse it of failing to curb the activities of Salafi Islamists.