For the first time since the Arab Spring uprisings of 2011, relations between mainstream Islamists in government and radical Salafist Muslim activists have reached breaking point, sparking deadly clashes in two Tunisian cities.
The rupture between the Ennahda party, the Tunisian arm of the Muslim Brotherhood which governs in coalition with secular parties, and the Ansar al-Sharia movement could have ramifications across North Africa, potentially fuelling armed insurrection in Tunisia and neighboring Algeria.
Clashes between police and Ansar supporters on Sunday, in which one person was killed and dozens wounded, highlighted the rise of fundamentalist Salafist groups in the nascent North African democracy, empowered by a new atmosphere of freedom.
The violence erupted after the government banned an annual preaching rally in the central city of Kairouan, a historic center of Islamic learning, and other towns. A young man was killed in the Ettadamen district of the capital Tunis.
"It seems like Ennahda have finally put their foot down, but that shouldn't be applauded because over the last two years they have tolerated the growth of Salafism and done nothing about it," said Aaron Zelin, an expert on Tunisia at the Washington Institute for Near East Policy.
"There is likely to be more confrontation in the short to medium term," he said. "There could be a cycle of low-level conflict, but neither side has an interest in it becoming larger-scale."
While many Salafists were jailed under the authoritarian rule of former President Zine El Abidine Ben Ali, they have benefited from the freedom created by the revolution that toppled him in January 2011.
Ansar al-Sharia is the most radical Islamist group to emerge in what was long one of the most secular Arab countries. It poses a test to the authority of the moderate Islamist-led government and to the stability of Tunisia, a country of 11 million.
Zelin estimated that the movement, which is not officially registered, has at least 20,000 activists and is gaining support fast among young people disenchanted with Ennahda's failure to anchor Islamic sharia law in the constitution, and alienated by unemployment and lack of economic opportunity.
Ansar's spokesman, Saif Eddine Rais, said last week the group had "tens of thousands" of supporters. Easy to recognize in their bright orange vests, its followers engage in proselytizing and charity work, providing food, medicines and community support in areas where the state is often absent.
The clashes were not the first bout of fighting between Salafists and police. This time, however, the government showed its determination to crack down on the radicals as it deployed mass force to prevent the public meeting.
The standoff came as the army pursued dozens of suspected al-Qaida-linked militants near the western border with Algeria. The government accuses Ansar al-Sharia of links to al-Qaida, although the Salafists dispute this.
"Salafists have felt targeted and this has only added to their frustration," said Alaya Allani, a specialist on Islamist groups. "These events are slowing [Tunisia's] democratic transition and delaying the recovery from an economic crisis."
A smaller, more moderate Salafist party, Hezb Ettahrir, had condemned the violence.
Tunisia was the first country to stage an "Arab Spring" uprising, inspiring similar revolutions in Egypt and Libya. It has since sought to ease economic and financial problems.
The Salafists, who model their lifestyle on the Prophet Mohammad and his companions, seek a broader role for religion in public life, alarming a secular elite that fears such a move would undermine individual freedoms, women's rights and democracy.
In a sign they do not recognize the state, protesters on Sunday burned Tunisian flags and in some places replaced them with a black banner in support of Al-Qaida. Chants included "The rule of the tyrant must fall" and "Join the Muslim army."
Ansar al-Sharia, whose fugitive leader Saifallah Benahssine — also known as Abu Iyadh — is a former al Qaeda fighter in Afghanistan, is seeking to establish an Islamic state in Tunisia and says democracy is blasphemous.
At a news conference ahead of the planned rally, spokesman Rais said: "Now we have institutions, the structure and we are preparing ourselves to apply the law of God in Tunisia. We will only take part in elections if only Islamists can participate."
Rais was arrested in Kairouan on Sunday and Ansar al-Sharia has called for protests on Friday to demand his release, possibly setting up another round of clashes.
In September, thousands of Salafists attacked the U.S. embassy. Four people were killed in the disturbances, which began as a protest over a film that mocked the Prophet Mohammed. Benahssine has been in hiding since then.
Salafists have also attacked cinemas and wine vendors, picketed secular cultural events and universities, and burned Sufi Muslim shrines. But so far there have been few arrests despite pressure from the United States and former colonial power France.
Police also blame a Salafist who is on the run for the assassination of secular opposition politician Chokri Belaid on Feb. 6, which provoked the biggest street protests in Tunisia since the overthrow of Ben Ali.
The latest crackdown came after the army said 10 Tunisian soldiers were wounded near the Algerian border in mine explosions in the Jebel Chaambi mountain region where Islamist militants are said to be setting up a training camp.
In the past few months, police have found large caches of weapons in Tunis and other cities and arrested 16 militants who they said were seeking to establish an Islamic state.
Prime Minister Ali Larayedh said on Saturday Ansar al-Sharia was linked to terrorism, although the authorities have produced no proof. The same day, the regional arm of al Qaeda issued a statement urging the group to defy the crackdown.
Many Tunisians say they fear for their peace and civil liberties if radical groups become too powerful.
"The revolution gave Salafists freedom and they want to impose their way by force," said Alia Sassi, 24, who works in a travel agency. "There is a real fear jihadis will pass onto bombings. We want to live in peace, we don't want our country to become a new Afghanistan."
Ennahda faces a balancing act. If it arrests more Salafists and forces Ansar al-Sharia underground, it could drive more young Tunisians towards violence, harming the economy and alienating its own more conservative wing.
Ennahda's veteran moderate leader Rachid Ghannouchi left the door ajar last week, saying "I am always for dialogue with the Salafists if they don't carry arms and want to talk, but there can be no dialogue now with terrorists who are carrying arms in Jebel Chaambi."
Diplomats say neighboring Algeria, which fought a decade-long civil war with Islamists in the 1990s in which more than 150,000 people died, is deeply concerned and has reinforced army units at the Tunisian border.
"Algeria is clearly very worried and feels almost a siege mentality," Zelin said, noting that the overthrow of Muammar Gaddafi in Libya in 2011 and French military intervention against al-Qaeda-affiliated Islamist rebels in Mali this year had increased the flow of weapons and fighters onto its soil.
Paradoxically, Egypt's Salafists have taken the opposite direction to their Tunisian counterparts.
All the main radical Islamist movements, including those involved in armed struggle in the 1990s and the assassination of former President Anwar Sadat, have renounced violence and joined the political system, and none has lent support to al Qaeda militants operating in the lawless Sinai Peninsula.
Indeed, the largest Egyptian Salafist group, the Nour party, is seeking to project itself as more democratic and open than the ruling Muslim Brotherhood.