Tunisia's political crisis is deepening after the assassination of a leading opposition leader earlier this week.
The killing of anti-Islamist politician Chokri Belaid sparked violent protests. The prime minister then announced a new, technocratic government.
But the governing Islamist party Ennahda rejected the move, saying PM Hamadi Jebali "did not ask the opinion of his party".
Ennahda denies opposition claims that it was behind Wednesday's killing.
In a separate development, lawyers and judges across Tunisia have launched a two-day strike in response to the killing, according to the AFP news agency.
Earlier, four opposition groups - including Mr Belaid's Popular Front - announced that they were pulling out of the country's national constituent assembly in protest.
Mr Belaid's killing has brought to a new pitch a long-simmering political crisis in Tunisia, with secularists and liberals accusing the Islamists of amassing too much power, the BBC's Sabastian Usher says.
New revolution calls
"We in Ennahda believe Tunisia needs a political government now," party Vice-President Abdelhamid Jelassi said on Thursday.
"We will continue discussions with others parties about forming a coalition government," he added.
Ennahda spokesman Abdelhamid Aljallasi later added that party members had not been informed of the prime minister's decision before he announced it.
Mr Jebali on Wednesday said he would dismiss the current cabinet and form a government of "competent nationals without political affiliation".
The new ministers would have a mandate "limited to managing the affairs of the country until elections are held in the shortest possible time," the prime minister said in a nationally televised address.
The killing of Mr Belaid - the first political assassination in Tunisia since the Arab Spring uprising in 2011 - sparked angry protests across Tunisia.
He was shot dead at close range in the capital, Tunis, on Wednesday. The attacker fled on the back of a motorcycle.
Thousands of people later rallied outside the interior ministry, many chanting slogans urging the government to stand down and calling for a new revolution.
In the centre of Tunis, a police officer was killed during clashes between police and opposition supporters protesting against Mr Belaid's death.
Mr Belaid was a respected human rights lawyer, and a left-wing secular opponent of the government which took power after the overthrow of long-serving ruler Zine el-Abidine Ben Ali.
Current President Moncef Marzouki said the assassination should not affect Tunisia's revolution.
"There are many enemies of our peaceful revolution. And they're determined to ensure it fails," he said.
Referring to Mr Belaid as a "long-standing friend", he said his "hateful assassination" was a threat.
"This is a letter being sent to us that we will refuse to open," the president said.
Mr Marzouki also announced that he was cutting short a visit to France and cancelling a trip to Egypt to return home to deal with the crisis.