The Islamist party dominating Tunisia's ruling coalition rejected the initiative of its own prime minister to form a non-partisan technocratic government on Thursday, extending the political crisis sparked by the assassination of a prominent leftist politician.

The announcement throws into question efforts to resolve one of the worst crises Tunisia has faced since its revolution and suggests divisions not just between the government and opposition, but within the ruling party itself.

Chokri Belaid, a fierce government critic, was shot several times in his car just outside his home Wednesday morning by unknown assailants. Demonstrations erupted around the country and were quelled by tear gas.

Prime Minister Hamadi Jebali announced late Wednesday that he would dissolve the government and form a new one of technocrats to manage the country until elections — a longstanding opposition demand that was widely welcomed.

But today, Abdel-Hamid Jalasi, the vice-president of Tunisia’s leading Islamist party Ennahda, said the party disagreed with the move and would not toss away the legitimacy it had gained in the country's elections.

"The position of Ennahda is that the troika (the three party ruling coalition) will continue to lead the country but it is open to a partial ministerial re-shuffle," party spokesman Abdallah Zouari told The Associated Press.

Tunisia's Radio Mosaique meanwhile reported full-scale riots in the southern mining city of Gafsa, where Belaid's Popular Front coalition of leftist parties has a great deal of support. Demonstrators marched through the city and threw stones at police, who responded with tear gas.

Eyewitnesses told Reuters that police in Tunis, the country’s capital, had fired tear gas to disperse protesters on Thursday.

Tunisia’s main labor union also declared a general strike for Friday over the assassination, a provocative move that is set to shut the country down and could further inflame tensions.

Year-old Tunisian government in trouble

Protests continue in Tunis following the assassination of opposition politician Chokri Belaid. (Anis Mili/Reuters)

There had been political trouble brewing in Tunisia — the country widely regarded as the birthplace of the Arab Spring after it toppled longtime President Zine El Abidine Ben Ali in January, 2011 — before the assassination. Relations between the government and the opposition had deteriorated in recent months and talks over a government reshuffle had gone nowhere.

Critics like Belaid accused the government of employing thugs to attack meetings of the opposition.

Belaid's family and associates claim the Ennahda Party is complicit in the assassination, and other opposition figures have claimed there is a list of potential targets.

Opposition parties had hailed the prime minister’s idea to dissolve the government in favour of one run by technocrats. Tunisia’s year-old government has often been criticized for being unable to tackle the country's problems, chief among them high unemployment and an economy battered by Europe's financial crisis and too few tourists.

"It's a recognition of the need to totally change the government which is incapable of running the country," said Taieb Baccouche, secretary general of the right-of-centre Nida Tunis (Tunisia's Call) party, one of the main opposition parties.

"There has to be immediate consultation between all the parties involved to avoid unilateral decisions."