By Abigail Hauslohner, Updated: Wednesday, February 6, 12:39 PM

Belaid warned at a news conference Tuesday that Tunisia could soon be engulfed by political violence, and he called for a national conference to address the subject.

Ennahda issued a statement calling Belaid’s death a “heinous” crime,and vowed to bring the perpetrators to justice, the Associated Press reported. The party said it “holds the conspiring parties behind this crime fully responsible and calls on security authorities to make all possible efforts to find the criminals and bring them to justice.” Prime Minister Hamadi Jebali told Agence France-Presse the killing was an act of “terrorism.”

Tunisian President Moncef Marzouki also expressed shock in a statement on his Facebook page Wednesday. He called on Tunisians to exercise “self restraint, and not to be hasty in analyzing this crime and cowardly act or to blame one side or another for it.” He said law enforcement authorities should investigate promptly and thoroughly, and bring those responsible for the killing to justice.

Tunisia’s Salafists have carried out a spate of attacks over the past year on liberal intellectuals, artists, human rights activists and journalists. They have also attacked alcohol sellers, art exhibits, movie theatres and shrines. They are accused of carrying out an attack on the U.S. Embassy in Tunis in September, allegedly in retaliation for an anti-Islam film that was produced in the United States.

The Salafists, who have called for the implementation of Islamic law in Tunisian society, have mostly rejected participation in the country’s still nascent democracy. Belaid and other opposition members had accused a shadowy group of Salafist militias, who call themselves “The Leagues for the Protection of the Revolution,” of being behind much of the violence. Even though Ennahda takes a markedly more moderate approach, watchdog groups say the government seems hesitant to crack down on the more extreme Islamists.

Complaints filed by the victims of alleged Salafist violence to Tunisia’s police force and judiciary, for example, rarely yield serious investigations and prosecutions, said Eric Goldstein, the deputy director of the Middle East and North Africa for Human Rights Watch.

“There is a climate of laxness toward violence in Tunisia,” Goldstein said. The government’s “response to these attacks by Salafi groups is that it’s better to have dialogue with them and bring them into the political process rather than throw them in jail.

“Sooner or later, they’re going to have to deal with extremists in their country and violations of their laws. . . . Let’s hope this is the wake-up call.”

In a news conference Wednesday afternoon, Popular Front leaders drew attention to Belaid’s calls for a national conference to combat violence. The Front said Belaid “felt threats to his personal safety” and was warned by a colleague as late as Tuesday that “armed people are after him.”

A number of Belaid’s colleagues accused Ennahda on Wednesday of being behind Belaid’s assassination. “The people who killed [him] are being adopted and cared for by the people in power,” Popular Front member Hamma Alhammami said at a televised news conference.

Clashes erupted between rock-throwing protesters and security forces, who fired tear gas, in downtown Tunis and outside the country’s Interior Ministry on Wednesday afternoon.

Television footage from earlier in the day showed angry crowds of Belaid’s supporters swarming an ambulance outside a clinic as his lifeless body was loaded into it for transport to a different hospital.

Sharaf al-Hourani in Cairo contributed to this report.