THE Islamist-led government that has been running Tunisia for the past year has been badly shaken by the assassination on February 6th of a prominent secular-minded opposition leader, Chokri Belaid, who was shot dead outside his house in Tunis by assailants so far unknown. After a wave of angry protests erupted in the capital and across the country, the prime minister, Hamadi Jebali, who is also secretary-general of the Islamist Nahda party, condemned the murder as an “act of terrorism…against the whole of Tunisia” and said he would form a new government “of competent figures without party affiliations”. The event has sparked Tunisia’s worst crisis since the revolution that toppled the country’s long-serving, secular-minded dictator, Zine el-Abidine Ben Ali, who fled into exile in January 2011.

It was unclear if Mr Jebali’s hasty reaction meant that Nahda, which handsomely won an election to a constituent assembly in October, 2011, would actually cede power or whether there would merely be a government reshuffle; it already heads a three-party coalition that includes non-Islamists. Mr Jebali has urged the constituent assembly to hurry up and finish the writing of a new constitution so that there can be a fresh election to a proper parliament as soon as possible, perhaps by the end of June.

The secular opposition, which is striving to present a united front, has called for a completely “new government”. It has suspended its participation in the constituent assembly and called a general strike to coincide with Mr Belaid’s funeral on February 8th.

Bad blood between the Islamists and more secular-leaning Tunisians has been stirring dangerously in the past few months. Many Tunisians who fear a creeping Islamisation of society have been quick to blame Nahda for complicity in Mr Belaid’s assassination.

In the past few months Islamist thugs have been taking the law into their own hands. Neighbourhood “committees to defend the revolution”, often including Nahda members who were political prisoners under Mr Ben Ali, have been accused of trying to intimidate opposition parties and have incurred growing hostility from more secular types. In December they violently broke up a trade-union rally.

Nahda has been accused of pandering to other groups of fringe Islamist extremists, who have gone out of their way, among other acts of intolerance, to attack ancient shrines long venerated by Tunisians, deeming them to be idolatrous. Since the revolution of 2011, at least 40 have been set alight or damaged.

Last month a clutch of Tunisians gathered in a courtyard of the Medina, the capital’s old city, to mark the Prophet Muhammad’s birthday with chants, drums and the clatter of iron castanets. They were honouring Sidi Ali Lasmar, a local saint venerated since the 18th century. Cowrie shells, a sequinned fish and the Tunisian flag decorate the walls of his shrine. Mixing elements of African culture from south of the Sahara, the cult has long held an exotic appeal for many people in Tunis.

At the other end of the alley, a vanload of police was poised to ward any Islamist extremists off. The veneration of local saints across north Africa harks back to pre-Islamic Berber and sub-Saharan cultures. Muslim reformists in 19th-century Tunisia dismissed such traditions as demeaning and superstitious. Under Habib Bourguiba, the country’s first president after its independence from France in 1956, many shrines were turned into museums, cultural centres or even cafés.

Others were officially tolerated for giving succour to people with medical or psychological worries. Nahda, which is close to the Muslim Brotherhood, has proclaimed an “Arab and Islamic identity”, implying distaste for shrine worship. But the desecrations obliged them to declare their respect for Tunisia’s diverse cultural and ethnic heritage.

Mr Belaid’s murder has dramatically raised the political temperature. Nahda, which has been sending out mixed signals, has been losing popularity. If Mr Jebali keeps his post, he and his Nahda colleagues will have to move fast to dispel suspicions that they are lenient towards violent Islamists. Unless they do so, Tunisia, once the most hopeful of the Arab countries to undergo revolution, could slide into instability. For Islamists, in Tunisia and beyond, it has raised fears that the Arab awakening that began in Tunisia more than two years ago could turn into an Arab nightmare.