Salafist Muslims tried to prevent the filming of current Internet craze the "Harlem Shake" at a Tunis school on Wednesday, but were driven off after coming to blows with students, an Agence France Presse correspondent said.

When the dozen or so ultra-conservative Muslims, some of them women in veils, showed up at the Bourguiba Language Institute in the El Khadra neighborhood, a Salafist bastion, students shouted "Get out, get out!"

Al-Baghdadi al-Mahmoudi, the last premier of deposed Libyan leader Moammar Gadhafi, is in critical condition after being tortured in a Libyan prison, his Tunisian lawyer said on Wednesday.

Mahmudi "is in critical condition as a result of the torture he has suffered," said Mabrouk Kourchid, adding that "he could die".

Tunisia's ruling Islamists said Wednesday they have agreed to give up key ministries to independents, a concession that could speed up the formation of a new government and end a political crisis.

"We confirm the 'neutralization' of the four sovereign ministries," Ennahda party leader Rached Ghannouchi said on Radio Kalima, referring to the interior, justice, foreign and defense portfolios.

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 suspected killer of leftist opposition figure Chokri Belaid, a leading critic of Tunisia's ruling Islamists whose murder sparked a political crisis, was arrested on Monday, police sources said.

They said the suspect was arrested along with an alleged accomplice, both members of the radical Muslim Salafist movement. The main suspect, a 31-year-old furniture maker, was arrested in the Carthage suburb of Tunis.

Tunisia's prime minister-designate, Ali Larayedh, was to start work Saturday on forming a new government after his predecessor and fellow Islamist Hamadi Jebali stepped down in the face of a political deadlock.

Rached Ghannouchi, who heads the two men's Islamist party Ennahda, said the efforts were focused on enlarging the three-member ruling coalition to add another two parties.

The Tunisian authorities have arrested suspects in this month's assassination of leading leftist opposition figure Chokri Belaid, the interior minister said.

"The investigation has progressed to the point that suspects have been arrested," Ali Larayedh told reporters, without specifying the number of people detained.

Two Tunisian police were wounded in an exchange of gunfire with presumed Salafists on Thursday in Sidi Bouzid, the cradle of the country's uprising two years ago, a medical source said.

The shooting took place when police after a chase cornered four armed men in a mosque in the center of the town, which is a stronghold of the ultra-conservative Muslim group blamed for unrest around the country.

Tunisia was scrambling to find a replacement prime minister on Thursday and pull itself out of a major political crisis two days after Hamadi Jebali quit after failing to form a cabinet of technocrats.

The consultative council of Ennahda was to meet later to choose a successor to Jebali, the ruling Islamist party's number two, who ruled himself out following suggestions that he might be reappointed premier.

Tunisia was in political limbo on Wednesday as President Moncef Marzouki suffered setbacks in his bid to replace Prime Minister Hamadi Jebali, who quit after failing in his plan to form a non-partisan cabinet.

Talks between Marzouki and Rached Ghannouchi, head of Islamist Ennahda party, ended inconclusively, dashing hopes of a soon end to Tunisia's deepest political crisis since the revolt that ousted Zine El Abidine Ben Ali two years ago.