Details added (first version published at 05:51)
Gunfire erupted in the Tunisian capital Tunis just hours after Foued Mbazaa was sworn in as interim president on Saturday, dpa reported.
Tunisian journalists said it sounded like the army was moving against the presidential guard of longtime leader Zine el-Abidine ben Ali, who fled the country on Friday to Saudi Arabia.
Mbazaa, the former speaker of parliament, was sworn in as president as the 23-year autocratic presidency of Ben Ali ended in a popular uprising.
Looters prevailed in the commercial centres and prisoners ran amok after a fire. Under a state of emergency, army tanks patrolled the streets. Relief at Ben Ali's departure was tempered with concern over what lay ahead.
The French government vowed to stop movement of funds connected to Tunisian assets, to prevent family members of the ousted government from illegally enrichment.
Upwards of 50 people were reported killed when a prison in the coastal city of Monastir caught fire as part of a strike for freedom, medical sources and eyewitnesses said.
Mbazaa ordered his prime minister Mohamed Ghannouchi, who briefly took power on Friday, to propose a unity government with ruling party and opposition members to govern until the next elections, which must be held within 60 days, according to the constitution.
The opposition, which was neutered under Ben Ali's rule, has been demanding to play a part in running the country, saying the current administration is corrupt and tainted by the police killing dozens of demonstrators.
A rush to new elections raised concern for many Tunisians.
"If a new election is quickly held, then the oppoisition will not have time to organize itself ... Only the old guard will take power," said Elias Nefzaoui, 25, in Tunis.
An 1800-0600 curfew stranded hundreds of arriving passengers at the airport in Tunis. Restaurants ran out of food, and families bedded down on the floor. Many Tunisians were returning home from abroad out of concern for their families.
A dozen arriving aircraft were expected through the nighttime hours.
Hundreds of European holidaymakers have fled the country. German tour operators cancelled all flights to Tunisia. Tourists returning home to Germany reported widespread destruction, plunder and destroyed petrol stations and police station.
"I was afraid," said Mbarka Khamassi of Baden Wuerttenberg after she arrived in Stuttgart.
Ben Ali fled after a month-long popular revolt that began when an unemployed school graduate trying to eke out a living selling vegetables fatally set himself alight in front of a government building on December 17. Officials had seized his produce.
The German government called for Tunisia to build a democracy, and Chancelleor Angela Merkel offered Germany's help.
The Jordanian government said it respected "the choice of the brethren Tunisian people" and pledged to stand with them in preventing the country "from sliding into chaos."
Jordan's opposition Islamic Action Front (IAF) hailed the toppling of Ben Ali and advised Arab leaders to quit "despotism" and speed up real political reforms in their respective countries.