Thousands of protesters rallied in the main government quarter in Tunis on Monday calling for Prime Minister Mohammed Ghannouchi to resign after the fall of veteran leader Zine El Abidine Ben Ali.

Security forces fired tear gas and sealed off the area with barbed wire as some protesters threw stones, charged police lines and smashed up a police car at the start of a make-or-break week for Tunisia's new transition government.

"Resign scum!" the protesters chanted after hundreds spent the night staking out the prime minister's offices in defiance of a curfew that has been kept in place in a bit to restore order amid continuing turmoil in the country.

Many of the protesters had made their way to the capital from the impoverished rural parts of Tunisia where the uprising began and held up pictures of victims of Ben Ali's bloody crackdown in recent weeks.

"We will stay a day, two days, a month, two months, as long as it takes for this government to quit," Ali Abassi, an unemployed man from the town of Menzel Bouzaiane, who said he was the brother of one of the victims, told AFP.

Many primary schools also remained shut despite a government order to re-open after teachers called an "unlimited" strike in protest against the national unity government installed after the end of Ben Ali's 23-year rule.

"This strike is irresponsible. Our children are being held hostage," complained Lamia Bouassida, one of dozens of concerned parents who had come to a school in the centre of the capital to see if it was open or not.

Teenagers in their final year of school returned to classes as expected.

The General Union of Tunisian Workers (UGTT), which called the strike, has refused to recognise the new government because it keeps in place key figures from the ousted regime including Prime Minister Mohammed Ghannouchi.

The UGTT said more than 90 percent of teachers were on strike.

"We support the demands of the people. The UGTT will never abandon the people in their struggle to demolish the old regime," said Nabil Haouachi, a representative of the teachers' union within the UGTT.

Many Tunisians feel the same way and have kept up daily protests since the government was announced last Monday, calling also for the destruction of Ben Ali's powerful RCD party, which has dominated Tunisia for decades.

Others say the revolution has gone far enough and it is time for calm.

"We have to make the democratic process real and irreversible and at the same time guard against the violence and anarchy that threaten our country," Rachid Sfar, a former prime minister, wrote in an editorial in La Presse daily.

Ghannouchi, who has been in place since 1999, has resisted pressure to quit and says he will resign from politics only after the north African state's first democratic elections since independence from France in 1956.

He said the vote could be held within six months but has not set a date.

France has been heavily criticised for offering support to Ben Ali during the violent crackdown by his security forces and President Nicolas Sarkozy on Monday said it had "underestimated" the anger of the Tunisian people.

A European Union official said there were also plans to boost economic aid to Tunisia from the 240 million euros currently budgeted for 2011-2013.

The Tunisian government has unveiled unprecedented democratic reforms including allowing full media freedoms, releasing political prisoners and registering political parties that were banned under Ben Ali.

The authoritarian strongman resigned and fled in disgrace to Saudi Arabia on January 14 under pressure from a wave of social protests against his regime.

The movement began after a 26-year-old fruit vendor, Mohammed Bouazizi, set fire to himself to protest police abuses in the farming town of Sidi Bouzid.

The Arab world's first popular revolt in recent history has inspired copycat self-immolations in Algeria, Egypt, Mauritania and Morocco.

There have also been calls for Tunisia-style protests in Sudan and Yemen.

The Tunisian government has sought to re-impose order and start up regular economic activity in the country following weeks of dramatic upheaval.

It has moved quickly against Ben Ali's relatives and loyalists.

On Sunday, the TAP state news agency said three key Ben Ali allies including Senate leader Abdallah Kallal were under house arrest while the head of the private Hannibal TV network was arrested for "high treason".