By Tarek Amara and Erika Solomon
TUNIS (Reuters) - Tunisian forces launched air and ground strikes on Islamist militants near the Algerian border on Friday after fierce overnight clashes in the area, which coincided with increased instability and political turmoil in the North African country.
Aircraft bombed caves in the Mount Chaambi area, where the military has been trying to track down Islamist militants since December, witnesses said on Friday.
"A major military operation with the participation of air and ground units began at dawn on Friday," army spokesman Taoufik Rahmouni said, adding that the army had surrounded a "terrorist" group of 15 to 20 militants.
"The army has now imposed a security ring around the area and is searching nearby towns in the region. Until now there are no casualties or arrests (in Mount Chaambi)," he said.
The operation was launched in the same area where militants ambushed and killed eight soldiers on Monday in one of the deadliest attacks on Tunisian security forces in decades. The gunmen slit the throats of some of their victims.
Tunisia's Islamist-led government is grappling with rising instability and a mounting protest movement organized by the secular opposition that is demanding its resignation. Rival rallies to support the ruling coalition have also been growing.
Prime Minister Ali Larayedh, who belongs to the Islamist Ennahda party, will discuss the security situation and the political crisis with opposition parties and other groups on Saturday, his office said. He is then expected to address the public.
An Algerian security source said that the militants in Mount Chaambi include Tunisians, Libyans and Algerians.
"They are heavily armed, likely with weapons from Libya," the source said. "We will do our best to support Tunisia but not intervene on its territory."
While the border fighting raged, pro- and anti-government protesters were preparing for a weekend of rival demonstrations. Protests have been mostly peaceful so far.
Tunisia's powerful union federation has called for the government to bow to opposition demands and create a new government within a week of starting talks with its rivals.
But the 600,000-strong Tunisian General Trade Union has endorsed Ennahda's demand that the transitional Constituent Assembly be allowed to finish drafting a new constitution and an election law, although it says the body must speed up its work.
The opposition, angered by the assassination of one of its leaders last week, wants the assembly dissolved.
Ennahda blames Salafi militants for that assassination and a similar one in February, as well as for two improvised bombs that exploded in Tunis in the past week, the first time such blasts in the capital. No one was hurt in the explosions.
In the town of Kasserine, near Mount Chaambi, security forces raided a mosque and arrested 12 Salafis, a witness said.
The porous border area is known for smuggling, which has flourished since Tunisians toppled autocratic President Zine al-Abidine Ben Ali in 2011.
The Interior Ministry said on Friday security forces had also arrested a Salafi militant who was preparing explosives in Manzel Bourguiba, a town 50 km (30 miles) north of Tunis.
Local media said the man was captured after blowing off his hand experimenting with explosives.
(Reporting by Erika Solomon; Editing by Alistair Lyon)