Tunisia mourned eight soldiers slain by militants, but appeals from the Islamist-led government for unity and the calling of a December election failed to quell sometimes violent protests.
Prime Minister Ali Larayedh reiterated that his government would not resign, telling the Wataniya 1 state television channel he was opposed "to this government stopping work".
The soldiers were found on Monday with their throats slit after they were ambushed by an armed group in Mount Chaambi near the Algerian border where the army has been tracking Al-Qaeda militants.
The brutal killings triggered protests in the nearby eastern city of Kasserine, where demonstrators ransacked the local office of the ruling moderate Islamist Ennahda party overnight, an AFP correspondent reported.
That incident came despite calls by President Moncef Marzouki for national unity and after Larayedh, an Islamist, announced a general election for December.
The election is seen as a concession aimed at appeasing a growing mood of rebellion in Tunisia, where emotions are running high since Thursday's assassination of a prominent opposition MP.
Many Tunisians want the government to go, believing it is responsible for the murder of Mohamed Brahmi -- the second opposition figure killed since February.
The North African nation, cradle of a wave of popular uprisings that swept the region, has been rocked by almost a week of violent anti-government protests.
Interior Minister Lofti Ben Jeddou told Mosaique FM radio he wanted to see a unity government.
"I considered handing in my resignation along with other security officials but in light of developments I decided to stay until the formation of a government that includes all the parties, and which will overcome their selfishness in order to meet the challenges and combat terrorism," he said.
But on Monday, Larayedh insisted his government would stay put.
"We are not clinging to power, but we have a duty and a responsibility that we will exercise to the end," he said, proposing instead a general election for December 17.
On Tuesday, Ennahda and several smaller parties moved to defuse the crisis by proposing that the ruling coalition be enlarged.
The signatories affirmed their "attachment to consensus and dialogue" and called for "widening the political base of power".
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Larayedh said he favoured enlarging the existing coalition.
"When I formed the government (in March), I had proposed a government of national unity," Larayedh said of talks that foundered as the opposition thought Ennahda wanted too much of a monopoly.
Ennahda coalition partner Ettakatol and the 500,000-strong General Union of Tunisian Labour (UGTT) separately called for a new government.
However, the powerful UGTT, a key player in the 2011 uprising, did not back the call by thousands of protesters who have demonstrated nightly outside the National Constituent Assembly calling for its dissolution.
Thousands of people gathered on the outskirts of the capital Tunis overnight Tuesday to Wednesday for rival demonstrations for and against the government, an AFP correspondent noted. But there were no reports of trouble.
Officials announced the deaths of the soldiers near the Algerian border just hours after Larayedh spoke on Monday.
State television ran pictures of the mutilated corpses of the victims, some of whom had their throats cut and had been stripped of their uniforms and weapons.
In a televised address, Marzouki, the secular president who is allied to Ennahda, called for national unity as his office declared three days of national mourning.
"If we want to face up to this danger we have to face up to it united," he said.
"I call on the political class to return to dialogue because the country, society, is under threat."
Since Brahmi's death, some 60 deputies have boycotted the assembly, which is drawing up the new constitution.
The government and UGTT stressed that deputies must return to work and vote on the much-delayed constitution, one of the thorniest issues in post-revolution Tunisia.
The proposed December 17 election date is loaded with significance.
It was on that day in 2010 that fruit vendor Mohamed Bouazizi set himself on fire in the town of Sidi Bouzid, sparking the the revolution that less than a month later had ended veteran strongman Zine El Abidine Ben Ali's 23-year grip on power.