Tunisia's army pressed operations against Islamists in a remote mountain range on Saturday after a deadly ambush on its troops heightened a crisis sparked by a political assassination.
This came as a coalition of opposition parties called for a rally to be held on Tuesday to demand the departure of the Islamist-led government and the dissolution of the National Constituent Assembly.
The parties chose the date for their planned march to fall exactly six months on from the assassination of opposition politician Chokri Belaid in February.
On July 25, a second opposition figure, MP Mohamed Brahmi, was also shot dead outside his home in a Tunis suburb, and authorities have said the same gun was used to kill both men, blaming jihadists for the murders.
Authorities, however, were tight-lipped about ground and helicopter raids on Friday in the Mount Chaambi area near the border with Algeria where Islamist militants, including veterans of a revolt in northern Mali, are suspected to be hiding.
Eight Tunisian soldiers were found in the area on Monday with their throats cut after being ambushed by militants.
Tunisian Prime Minister Ali Larayedh refused to discuss the operation during a news conference but stressed the need for "national unity" and reiterated that his government will not step down.
Larayedh's ruling Ennahda party has called for a mass solidarity rally in Tunis to insist on its "legitimacy to govern" as opponents have staged nightly anti-government demonstrations over the past week.
Meanwhile, the interior ministry said a "religious extremist" was killed and another wounded in two separate incidents while handling explosives.
And police said a suspect package was found in Tunis containing a letter warning security forces to withdraw from Mount Chaambi.
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The coalition government led by the moderate Islamic movement Ennahda has acknowledged that the country faces a growing threat from terrorism.
But interior ministry spokesman Mohamed Ali Aroui insisted on Saturday that there was no "specific" threat of terrorist attack.
"The risk of an attack is the same in Tunisia as it is in France or anywhere else in the world," he told AFP.
Ennahda has rejected mounting calls from its detractors who are urging it to quit for failing to prevent the murders of Belaid and Brahmi, and for its inability to rein in radical Islamists.
The party which emerged victorious in the October 2011 elections has proposed, however, to enlarge the coalition government.
Radical Islamists have grown in influence since the 2011 uprising that toppled long-standing president Zine El Abidine Ben Ali, and have been blamed for a wave of violence over the past two years.
Since Brahmi's death around 60 politicians have pulled out of the National Constituent Assembly that is drawing up Tunisia's long-delayed new constitution.
One of them, Karima Souid, told AFP on Saturday that Tunisia needed a "national salvation government."
"The opposition does not want to govern but would like... the formation of a national salvation government," she said.
Tunisian authorities have pointed to links between the Chaambi militants, the assassins of Brahmi and Belaid and Tunisia's main Salafist organisation Ansar al-Sharia, which denies the accusation.