Tunisia's Islamist-led government will not step down despite opposition demands, the prime minister has said.
Ali Larayedh said it would fulfil its mandate and hold elections in December.
He was responding to anger over the murders of two leading politicians by suspected Islamist militants, including the assassination of an MP on Thursday.
As the political crisis continued, officials said that at least eight soldiers had been killed by gunmen near the Algerian border.
There were reports that some of the soldiers' throats had been cut, in what is thought to be one of the worst attacks on the military in decades.
The attack took place in the remote Mount Chaambi area, where troops have been searching for hideouts of suspected al-Qaeda-linked militants.
Tunisian TV suspended normal programming, and President Moncef Marzouki declared three days of mourning for the soldiers.
'Not clinging to power'
There have been further clashes in Sidi Bouzid, where the uprising that overthrew the previous administration in 2011 started.
The secular Ettakatol party had called for the coalition, led by the Islamist Ennahda party, to step down because of the tensions following the killing of Mohamed Brahmi, the leader of the small left-wing Popular Movement party.
"We have called for the dissolution of the government in favour of a unity government that would represent the broadest form of consensus," Lobni Jribi, an Ettakatol leader, told Reuters news agency.
In February, the murder of prominent secular figure Chokri Belaid sparked mass protests and forced then-Prime Minister Hamadi Jebali to resign.
In a televised speech, Mr Larayedh insisted the government was not simply trying to hang on to power in the wake of the furore over the murders.
"This government will stay in office: We are not clinging to power, but we have a duty and a responsibility that we will exercise to the end," the AFP news agency quotes him as saying.
He said the transitional government planned to hold elections by the end of 2013, setting the date for 17 December.
Mr Brahmi's death last week plunged Tunisia into another political crisis, with rival demonstrations taking hold in several cities, including the capital.
Thousands of people demonstrated in front of the national assembly in Tunis on Monday demanding the government's resignation.
The interior ministry said a crowd of up to 25,000 people - both supporters and opponents of the government - gathered outside the assembly.
Also on Monday, crowds of protesters clashed with police in Mr Brahmi's home town of Sidi Bouzid, widely considered the cradle of the 2011 revolution that toppled former President Zine al-Abidine Ben Ali.
In both cities, police reportedly fired tear gas to disperse the protesters.
Dozens of legislators have already withdrawn from the national assembly and called for the Islamist-led government to be replaced by a national unity administration.
They consider Mr Brahmi's killing a failure of government to protect its citizens.
The governing Islamist Ennahda party stands accused by its opponents of failing to rein in radical Islamists in the country.
Since coming to power, it has faced growing unrest - particularly among the youth - over a faltering economy and a rising radical Islamist movement.