Former Tunisian President Zain El-Abedine Ben Ali quit office after 23 years in power and fled the country after handing over authority to his prime minister, Al Arabiya reported.
Tunisian Prime Minister Mohammed al-Ghannouchi announced that he has taken over the authority as interim president, the Tunisian TV said.
"Starting from now, I will be in charge of all the duties of the presidency," Ghannoushy said. He called upon the Tunisian people to unite and vowed to respect the constitution and restore stability in the country.
State of emergency
Earlier on Friday, Tunisia has been placed under a nationwide state of emergency, with the army taking over control of security from the police, state television reported.
The government placed Tunis, the capital, under curfew for a third night, banning public gatherings and authorising security forces to fire on anyone refusing to obey orders.
The measures came after protesters demanding the ouster of President Ben Ali clashed with security forces, leaving scores of people dead.
The army took control of Tunisia's main international Tunis Carthage airport and the country's airspace was shut down, an airport source told AFP.
"I can confirm that the army is at the airport. Armoured vehicles are surrounding the airport," the source said when asked about rumours that members of President Ben Ali's circle were about to flee the country.
"The airspace is closed too," the source said on condition of anonymity.
Ben Ali earlier in the day sacked his government, dissolved the parliament and called for early elections in six months' time, the official TAP news agency announced, as weeks of unrest mounted.
Ghannouchi, quoted by the official TAP news agency, said Ben Ali had decided among measures announced late Thursday to calm the unrest "to dismiss the government and call early elections in six months."
He said he had been tasked with forming a new government.
Earlier on Friday, thousands of people gathered outside Tunisia's interior ministry to demand the immediate resignation of Ben Ali.
The crowd were shouting slogans including: "Ben Ali, leave!" and "Ben Ali, thank you but that's enough!"
After nearly a month of riots that initially focused on unemployment, sparked by the suicide of a young graduate who set himself alight, the president had appeared on television Thursday in a bid to calm tensions.
He promised he would not seek another term in office and vowed to liberalize the political system.
Medical sources, meanwhile, said that security forces shot dead 13 people in the Tunisian capital and suburbs late Thursday, after President Ben Ali said he ordered police to stop firing on protesters.
"The bodies of three people struck with bullets were taken to the hospital at Kram, close to Tunis, and 10 others have been brought to Charles Nicole hospital in Tunis," one source told AFP Friday.
The figure was confirmed by another medical worker who took part Friday in a major demonstration against Ben Ali in the city center and was dispersed by police firing volleys of tear gas.
Tunisia's opposition reacted positively on Friday to Ben Ali's pledge not to seek another term in office and to his promise to liberalize the political system.
"The positive fact is that the president decided not to stand again" said Mohammed Nejib Chebbi, long-standing leader of the Progressive Democratic Party, which is legal but not represented in parliament.
Chebbi said the situation was “very dangerous” and it was possible the demonstrators could take over the interior ministry. He called for an “immediate peaceful solution” before bloody clashes return to the streets.
In his state of the union speech, Ben Ali vowed not to stand for re-election in 2014 and said his forces should no longer use lethal force against demonstrators, after rights groups said at least 66 people had been killed.
Following foreign criticism of the country's democratic record, Ben Ali promised to introduce "total freedom" of information and Internet access and vowed reforms.
"I say again to you here that I want to deepen democracy and to revitalize pluralism in our country," he said.
The president promised to lower prices of basic commodities such as milk, bread and sugar.
"This speech opens up possibilities," declared Mustapha Ben Jaafar, head of the Democratic Forum for Work and Liberties.
He added, however: "These intentions still have to be applied."
I say again to you here that I want to deepen democracy and to revitalize pluralism in our country
President Zine El Abidine Ben Ali
Member of Parliament Ahmed Ben Brahim, head of the former communist Ettajdid party, said: "It's positive, the speech answers questions that were raised by our party."
Human rights militant Bouchra Bel Haji, said Ben Ali had "freed us and freed himself."
But not everyone was so positive, with another human rights defender Mohamed Abbou declaring he did not believe the president and that Ben Ali was "fooling the Tunisians with promises that have no tomorrow".
A contrite Ben Ali, 74, who has ruled the North African country with an iron fist for the last 23 years, said that he did not intend to scrap a constitutional upper age limit for candidates.
"I say no to being president for life and I refuse to alter the age limit set by the constitution," he added.
"Enough firing of real bullets," he said, adding in a rare admission that he had been "wrong" in his analysis of the country's social ills and promising a full inquiry to establish "each and everyone's responsibilities".
But even as the president addressed the nation, two people were killed as police opened fire on protesters in central Tunisia, witnesses said.
The witnesses, who asked not to be named, spoke of chaos in the town of Kairouan where pillaging had taken place over several hours.
Near Tunis, in the El Ghazala neighbourhood, clashes took place late Thursday between the police and demonstrators around a technological centre guarded by the army, an AFP journalist said.
I say no to being president for life and I refuse to alter the age limit set by the constitution
The government plans to provide grants and health coverage to holders of higher-education certificates on condition that they participate in cultural, sports or developmental activities, Ghannouchi said.
Unemployment in Tunisia is forecast to reach 13.1 percent in 2011 even as the economy grows 4.8 percent, according to the International Monetary Fund.
President Ben Ali on Jan. 10 blamed outside powers and masked gangs for the demonstrations.
Ben Ali, in the post since 1987, has pledged that by the end of 2012 the government will provide jobs to all graduates who have been unemployed for two years, boosting the number of jobs created by then to 300,000. Provincial companies that recruit young people to fill at least 10 percent of their jobs will be exempt from taxes on profits, he said.