After weekend clashes with the moderate Islamist government led by the once-outlawed Ennahda Party, the militants seem set to plunge the former French colony into the upheaval that's gripping its neighbors.
Egypt, Libya and Mali are in turmoil. Algeria, which has managed to evade the so-called Arab Spring, is under threat.
As al-Qaida in the Islamic Maghreb, the main jihadist group in the region, battles French-led forces in northern Mali and spreads across North Africa, there are fears of growing militancy in Tunisia, long seen as secular model for its neighbors.
But Tunisian militants were the largest contingent in an attack by some 40 fighters from an AQIM splinter group on the In Amenas desert gas complex in Algeria in January.
Although Tunisia's a relatively small country in the western Mediterranean, over the years it has produced a disproportionate number of jihadist militants who fought first in Afghanistan against the invading Soviets in 1970-89, then Iraq and now in Mali and Syria.
Regional security sources say hundreds of Tunisians have gone to join the jihadist rebel forces led by the al-Nusra Front in Syria's civil war.
Hard-line Islamists were allegedly behind the assassination of secular politician Chokri Belaid on Feb. 6 outside his Tunis home, the first political assassination in Tunisia in a decade.
That killing triggered the biggest street protests since the January 2011 overthrow of President Zine al-Abedine Ben Ali, the first Arab dictator to fall in the chain of pro-democracy revolutions that still convulse the Arab world.
Ben Ali, who fled to Saudi Arabia, was succeeded by a moderate Islamist-led government elected after the revolution.
It allowed hard-line Salafists to preach their puritanical brand of Islam, in the belief they would see no value in the kind of confrontation prevalent in other Arab states and wouldn't provoke violence.
Western and Arab diplomats say Ennahda's policy of tolerance strengthened the hardliners and encouraged them to believe they could get away with attacking journalists, artists and secular opponents.
The Salafists were allegedly behind an attack on the U.S. Embassy in Tunis Sept. 14, 2012.
In December, militants linked to AQIM seeking to smuggle arms across the border from Algeria clashed with Tunisian forces, leaving a dozen soldiers wounded.
But the patience of the government, led by the Ennahda party under Prime Minister Ali Laraydeh, ran out at the weekend when the militant Ansar al-Sharia group sought to defy a ban on its annual gathering in a Tunis suburb.
That triggered street clashes between the authorities and the Salfists in the capital and the central city of Kairouan. At least one protester was killed and scores of police officers were injured.
On Sunday, Laraydeh declared Ansar al-Sharia, a name used by al-Qaida in other Arab states to mask clandestine operations, an illegal organization that must obey the law "or end its existence."
The hard-liners' response has been one of defiance, raising fears of internecine conflict.
"You're making a foolish mistake because faith cannot be defeated by any force in the world," Ansar al-Sharia's leader, Seifallah Ben Hassine, declared in an online statement.
"I remind you that our youth, which proved its heroism in the defense of Islam in Afghanistan, Chechnya, Bosnia, Iraq, Somalia and Syria, will not hesitate to make sacrifices for the faith."
Hassine, aka Abu Ayyad al-Tunisi, is a veteran militant. He co-founded the Tunisian Combatant Group and fought in Afghanistan.
He's been in hiding since his organization was accused of the attack on the U.S. Embassy in 2012 and an assault on a U.S. school.
Much of North Africa is already a powder-keg, and if Tunisia, with a badly under-funded security force, becomes a battleground as well, the region will face intense conflict that could combine with the growing menace at the eastern end of the Mediterranean in the Levant.
There, the 2-year-old Syrian civil war, which began as an uprising against President Bashar Assad's minority regime, threatens to engulf neighboring Lebanon, Jordan, Iraq and possibly even Turkey in sectarian warfare between Islam's Sunni and Shiite sects.