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Tunisia is taking a harder line on preaching by ultraconservative Muslim groups, a crackdown that has sparked demonstrations by rock-throwing protesters and ominous warnings of terrorist attacks to come.

As it struggles to hunt down al-Qaida linked terrorists in its frontiers, the government has also been trying to rein in salafis emboldened by the fall of the country's repressive dictatorship two years ago. The interior minister said last week that gatherings will require permission, a measure rarely enforced in the past that is an attempt to stop tent meetings springing up around the country to build support for the groups.

One of the most vocal of them threatened Monday that if the government cancels its annual conference this weekend — an event attended by 40,000 last year that featured martial arts displays and sword-wielding horsemen — its adherents who have experience in jihad could strike.

"You are making a foolish mistake because faith cannot be defeated by any force in the world," said Seifallah Ben Hassine, the leader of Ansar al-Shariah, in an online statement. "I remind you that our youth that 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."

Tunisia's government, led by the moderate Islamist Ennahda Party, which won elections after the overthrow of Zine El-Abidine Ben Ali's secular dictatorship, had been criticized by the opposition for its permissive attitude toward the conservative religious movements that arose with the fall of the regime.

In the freedoms of the post-revolutionary period, these groups moved aggressively to gain supporters, alarming the more secular middle class in this country of 10 million. Ennahda Party members insisted they did not want to follow the old repressive policies of the dictatorship, but their tolerance for the salafis frayed as the groups became increasingly violent, attacking art exhibits, police stations, cinemas and the U.S. embassy.

Ben Hassine is in hiding for his alleged role in the Sept. 14 attack on the embassy in Tunis, in which several salafi groups converged, burning cars and destroying a nearby American school.

Tunisia has also been struggling to deal with the spillover from fighting in Libya, extremist groups in Algeria and bands of fighters fleeing the French intervention against al-Qaida linked groups in northern Mali. Last week, 16 Tunisian soldiers were wounded by roadside bombs as they combed a mountain range near the Algerian border for a militant group believed to have fled Mali, putting the country in a state of high alert and prompting the crackdown on gatherings.

"We will confront with the law, or if necessary by force, all people who attack the security forces or the institutions of the state," said ministry spokesman Mohammed Ali Aroui.

In defiance of the government over the weekend, salafis set up tents around lower-income Tunis suburbs and in conservative southern towns. When police attempted to dismantle the tents, they were met with stones and firebombs, and responded with tear gas.

A video of one such rally in the town of Menzel-Bourguiba, north of the capital showed several preachers calling for jihad into megaphones.

"No one can resist when the wind of revolution blows," said one speaker, accusing the government of being an American lackey. "You get on your knees in front of America, but our youth will bring America itself to its knees."

Ansar al-Shariah rocketed to prominence last year at its gathering in Kairouan, one of Islam's most revered cities. The Interior Ministry has yet to say if they will allow the conference to go head, but the group's spokesman said the government would bear responsibility for the consequences if it bans it.

"We will not march backwards," said Seifeddine Rais during an interview with Shems FM radio, in which he predicted at least 30,000 would attend.