At least eight Tunisian soldiers were killed on Monday when gunmen ambushed an army patrol in a mountainous region bordering Algeria.
"An entire patrol carrying out a search operation in this mountainous region was decimated," said presidential spokesman Adnan Mancer.
Reports said that three of the dead also had their throats slit and that the gunmen took the soldiers' weapons during the attack, which took place on Jebel Chaambi, Tunisia's highest mountain, at 5,000 feet.
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Mancer noted that reinforcement have been sent to the region. The army said it had been cleared of militants on June 24, after a two-month operation that left three dead and wounded 27.
Later on the same day as the ambush, a security patrol was hit by a landmine in the same area, injuring three soldiers.
The attacks come just five days after left-wing opposition leader Mohamed Brahmi was shot dead in front of his house.
Tunisian President Moncef Marzouki blamed Islamic militants and extremists for the violence. He announced three days of mourning for the victims and called for national unity in the face of terrorist attacks.
"It's our revolution that is being targeted, our way of life and our Islam that is the aim of these acts," he said.
"Are we going to let (the terrorists) realize the other half of their objectives and destroy the state?" he asked. "Today is the moment to come together for Tunisia, so that the blood of the martyrs is not shed in vain and to open a new page."