Tunisia’s acting president took power yesterday and pledged to free up the political system amid continuing unrest following the ouster of the north African state’s former authoritarian leader.

After being formally sworn into office to take over from Zine El Abidine Ben Ali, speaker of parliament Foued Mebazaa said that all Tunisians “without exception” would now be able to take part in national politics.

“A unity government is necessary in the greater national interest,” Mebazaa added, as the tightly-controlled country’s Constitutional Council declared that presidential elections should now be held in two months’ time.

The exiled head of the main Tunisian Islamist party told AFP that he now plans to return to his homeland.

“The Tunisian intifada has succeeded in collapsing the dictatorship,” Rached Ghannouchi, leader of the banned Ennahdha, said in London.

Security forces meanwhile imposed a harsh crackdown on suspected looters and locked down the heart of the capital Tunis to prevent further protests.

Tanks and armoured personnel carriers were deployed around the city.

In Monastir in central Tunisia at least 42 prisoners were killed in a fire after one inmate set his mattress alight in a failed escape bid.

There were reports of other attempted escape bids in prisons around Tunisia, as inmates apparently sought to take advantage of confusion in the country.

Several stolen cars were seen smashed and abandoned in the streets around Tunis and some shops and luxury homes had been pillaged and burnt, with the violence appearing to target in particular the property of Ben Ali’s family.

Ben Ali signed his resignation last Friday and fled to Saudi Arabia after a wave of protests sparked by the suicide of a 26-year-old graduate prevented by police from selling fruit and vegetables to make a living.

Human rights groups say dozens have been killed in the protests, which began last month and have since escalated into a popular uprising against unemployment, poverty and the alleged corruption of the ruling elite.

The Constitutional Council formalised the change of power, declaring that Ben Ali had “definitively” left power and appointed Mebazaa as interim head.

International powers, including European nations and the US, urged calm in Tunisia and called for a democratic process in the north African state after events that Tunisian internet users dubbed the ‘Jasmine Revolution’.

France, once one of Ben Ali’s closest allies and Tunisia’s former colonial overlord, said the people had “expressed their democratic will” and called for “free elections in the shortest time possible”.

German Chancellor Angela Merkel backed “real democracy” in Tunisia, coupled with respect for human rights and freedom of the press and assembly.

“I appeal to you to use this deep break in Tunisia’s history as a new departure,” she told the new authorities in Tunis.

The Arab League called on Tunisian political forces to unite and bring back peace, saying the events in Tunisia were “historic”.

The change of power in Tunisia was the first time in recent history that a leader of the Arab world has been toppled by pressure from street protests.

The revolt in Tunisia “is the first popular uprising to succeed in removing a president in the Arab world,” said Amr Hamzawy of the Carnegie Middle East Centre based in Beirut.

“It could be quite inspiring for the rest of the Arab world.”

Analysts said the abrupt change of power was likely to send shockwaves around a region dominated by veteran leaders like the 74-year-old Ben Ali.

Tunisia borders two other authoritarian regimes – Algeria and Libya.

A state of emergency has now been declared in Tunisia that bans demonstrations and imposes a strict dusk-to-dawn curfew, with orders given to security forces to shoot anyone disobeying orders or fleeing.

“It is unacceptable that the looting continues,” Prime Minister Mohammed Ghannouchi said in an interview on Al-Jazeera television.

“We are making every effort to restore order throughout the country.”

There was relief among many Tunisians over the toppling of the widely-hated Ben Ali, but also fears for the future of the country.

“After 23 years the people’s rage just exploded,” Farhat Hafayedh, 56, a retired factory worker in the town of Carthage near Tunis, told AFP.

“This is like the French Revolution... It’s the end of an era. I’m hoping there is real change. We can’t continue like this,” he said.