Radical Salafist Muslims murdered Tunisian opposition leader Chokri Belaid, with four suspects arrested and the killer identified but still on the run, Interior Minister Ali Larayedh said on Tuesday.

The breakthrough comes as Larayedh, named as prime minister-designate, presses efforts to form a new government aimed at pulling Tunisia out of a deep political crisis sparked by the February 6 killing of Belaid outside his home in Tunis.

“The killer has been identified and is being chased,” Larayedh told a news conference.

“Four other suspects have been arrested. They are Tunisians and belong to a radical religious strand … which we refer to as the Salafist movement,” said Larayedh.

Belaid’s daylight killing on February 6 sparked deadly street protests and strikes and exposed the widening fissures between the ruling Islamists and liberals.

It also threw Tunisia into its worst political crisis since the revolution two years ago that ousted strongman Zine El Abidine Ben Ali.

Larayedh said the four people arrested had “monitored (Belaid) for some time”.

One of the suspects, he added, “confessed to having accompanied the killer on the day of the crime.”

Police sources had earlier told AFP that those behind the killing were adherents of the Salafist movement, which is known for its radical version of Sunni Islam.