Tunisia's interim prime minister has raised the possibility of delaying elections in July for an assembly that will draft a new constitution.

The move could stoke anger among anti-government protesters who have pressed ahead with low-intensity demonstrations months after they forced Zine El Abidine Ben Ali, the long-serving president, to step down.

Beji Caid Essebsi suggested for the first time in a state television interview on Sunday that the ballot could happen later than July 24, although he stressed that the North African nation would still try to hold the vote on that date.

"If the reform committee says there would be technical difficulties that would be another probability to look at," Essebsi said.

The government still has to set up a promised independent electoral body to prepare for the ballot.

Tension is also growing in Tunisia which has struggled to restore stability since a revolution in January ousted Ben Ali and inspired uprisings across the Arab world.

The countdown to the election has been marked by fears among the secular establishment that a moderate Islamist group banned under Ben Ali could do well in the elections.

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Essebsi's comments came as police in the capital, Tunis, used tear gas to break up a fourth day of protests by scores of youths who have returned to the streets, many of them doubting the interim administration's promises to restore democracy after the uprising.

After a night curfew imposed to bring order, security forces clashed with bands of youths setting out to loot and pillage in the more densely populated parts of Tunis. Shots were fired.

The spark for the most recent protests was a warning from a former interior minister that there would be a coup d'etat if the Islamist group, al-Nahda, won the vote.

Essebsi reiterated the government's condemnation of the comments and described them as irresponsible.
    
Scores of protesters in the centre of Tunis called on Sunday for the resignation of Essebsi and his government, although the size of the demonstration was smaller than those on the three previous days.
   
Black-clad riot police fired teargas to push the protesters, some throwing stones, off the central Avenue Bourguiba.
   
The authorities dismiss suggestion that there will be a coup and have responded to the protests by imposing an overnight curfew. The move, which began on Saturday, is intended to ensure the safety of citizens, officials said.
   
Some Tunisians condemn the renewed demonstrations and want to see a return to normality in the country of 10 million, where the turmoil and war in neighbouring Libya are expected to cut economic growth to little more than one per cent this year.
   
"Those who are demonstrating are those from the lowest level who have nothing to lose," complained businessman Moez Hlcheri. "You can't have everything immediately. You have to work for it."