Tunisia's Islamist-led government was split yesterday as the ruling party rejected its own premier's declaration that he would dissolve the government and replace it with a board of technocrats.
The prime minister, Hamadi Jebali, made his decision after the assassination of a secular opposition leader.
The death of Chokri Belaid, shot several times in front of his house on Wednesday, has plunged Tunisia's fragile democracy into a crisis.
The moderate Islamist party Ennahda said it would not accept Mr Jebali's decision to make wholesale changes to the government.
Ennahda said the three-party ruling coalition would "continue to lead the country but it is open to a partial ministerial reshuffle", said spokesman Abdallah Zouari.
Its announcement throws into doubt its ability to stem the crisis in which thousands of people, convinced that the party was involved in Belaid's death, have filled the streets in the capital and across the country.
The powerful national trade union UGTT has called for a strike today to coincide with the funeral of Belaid, which is likely to be highly emotive.
Mr Jebali's proposal to present a new government of politically neutral figures to the assembly of elected officials, and for them to vote on the line-up, would greatly reduce Ennahda's power and influence.
It was by far the most successful party in 2011 elections, and has a number of key ministers, including Mr Jebali himself.
But Ennahda made a counter-move yesterday after long talks with the opposition, and unveiled a coalition of members of the assembly that includes several secular parties.
Bechir Nefzi, a member from the secular Congress for the Republic, one of the three parties in the current cabinet, said the group met yesterday and was drafting an "outline" for its purpose.
"This is not a political or electoral front, but one whose aim is defending democratic legitimacy," Mr Nefzi said on his Facebook page.
It now seems possible that if Mr Jebali were to present a new government to the assembly, he would fail to get a vote of approval for his plan.
The crisis is one of the most serious the country has faced in the two years since a popular uprising ejected president Zine El Abidine Ben Ali from power.
The long-repressed Ennahda party romped to victory in elections 10 months later, and has tried to rule the country in a coalition with two of the country's many secular political groups.
But the task has not been easy. The constitution remains unfinished and the economy deeply problematic, while divisions have deepened between rich and poor, religious and secular, coastal elite and rural poor.
The death of Belaid, whose killers have not been identified, brought simmering anger to a head as people chanted in the streets and protested outside Ennahda offices, as riot police fired tear gas at them.
"It's never been this polarised," said Zied Mhirsi, who co-founded the Tunisia Live website after the fall of Ben Ali.
"I think everybody blames Ennahda for the trouble. First, because they appointed incompetent ministers, second because there is a lot of clientelism, but also because they are not open to dialogue."
The unwillingness or inability to reach consensus in a country just becoming acquainted with democracy was, Mr Mhirsi added, also crippling the opposition, who have been vocal but disunited over the past two years.
The death of Belaid has created enormous pressure on Ennahda, he said, but fear of a similar fate may dampen the enthusiasm of some of his fellow opponents of the Islamists.
"Times are turbulent," said Radwan Masmoudi, from the Centre for the Study of Islam and Democracy in the capital, Tunis.
"I think it is ridiculous to blame Ennahda for having anything to do with the assassination. It would not only be stupid, it would be suicidal."
But Mr Masmoudi said political violence was a growing concern and the killing was deeply worrying.
"The political crisis is not a major problem," he said. "It's part of the democratic process. We are all learning what it means to govern … but there is a lot of fear of violence and that is a problem."
Mr Masmoudi was worried that whoever was behind the murder might strike again.
"We don't think this was a random act of violence," he said. "We think this was premeditated to derail the political process."
* With additional reporting by Associated Press