Tunisian President Moncef Marzouki's secular party Sunday quit the Islamist-led government, which is reeling from last week's assassination of secular opposition leader Chokri Belaid.

Belaid's killing on Wednesday - Tunisia's first such political assassination in decades - has thrown the country into turmoil, widening rifts between the dominant Islamist Ennahda (Renaissance) party and its more secular foes.

"We have been saying for a week that if the foreign and justice ministers were not changed, we would withdraw from the government," Samir Ben Amor, an official of Marzouki's Congress for the Republic Party (CPR), told Reuters.

The CPR has criticized the performance of the two ministers, one of whom, Foreign Minister Rafik Abdessalem, is the son-in-law of Ennahda leader Rachid Ghannouchi.

Ben Amor said the CPR's withdrawal was unrelated to Prime Minister Hamadi Jebali's decision, after Belaid’s death, to form a nonpartisan government of technocrats to run the country until elections can be held later in the year.

Leaders in Ennahda, as well as in its two non-Islamist coalition partners, objected to Jebali's proposal, saying he had failed to consult them first, Reuters reported.

Jebali said Saturday he would unveil his new Cabinet this week, and would resign if the parties don’t support it.

A senior Ennahda official, who asked not to be named, told Reuters the National Constituent Assembly would have the final say, but added: "We see that it will be possible to form a government of technocrats that includes political parties."

Ben Amor said Marzouki's CPR would formally submit the resignation of its three ministers to Jebali on Monday.

Political analyst Youssef Ouslati told Reuters the party was "trying to jump out of a sinking ship," but that its decision had no great weight because Jebali was now the central player.

He said that if political uncertainty continued, "the street will be the crucial element."

“The resignations are a pre-emptive strike in anticipation of Jbeli dropping them from the Cabinet,” Salem Labyad, a professor at the University of Tunis, told Bloomberg News. “The Congress’s decision will have no effect or political ramifications as Jbeli is insisting on forming a technocrat government.”

The country was relatively quiet Sunday after three days of nationwide protests following Belaid's death, the Voice of America reported. Riot police patrolled the streets of the capital, Tunis.

Few details are yet known about Belaïd's murder. There has been no claim of responsibility, and there is no clear indication of who may have been behind it. In a country with a mistrusted police force and justice system which remain largely unreformed since the revolution, there has been outrage at what represents a new kind of political murder: an assassination in broad daylight of a type not seen in Tunisia since colonial times.

Mokhtar Yahyaoui, a judge and human rights activist who has sat on the Council for the Safeguard of the Revolution told the Guardian: "There is a fear in political life which is a real challenge to Tunisia. It's essential for a full investigation, for us to know who is behind it, to put a line under it and calm everyone."

Belaid's funeral drew tens of thousands of mourners in Tunis and other cities on Friday in what turned into mass political protests against Ennahda and the government it dominates.

About 6,000 Ennahda supporters took to the streets of the capital on Saturday in a peaceful show of strength.

The CPR came a distant second in the December 2011 election, winning 29 of the assembly's 217 seats to Ennahda's 89, but Marzouki was elected interim president by the assembly in a show of unity and his party entered a coalition government led by Ennahda.

Belaid's widow Basma said Saturday she was asking the government to protect her family with official protection.

Some members of Belaid's family have accused Ennahda of being behind the shooting, something the party denies.

Ghannouchi, Ennahda's leader, has threatened legal action against politicians or journalists pointing the finger at him, saying they were "exploiting the blood of the deceased for narrow political ends at the expense of the truth".