Tunisia's prime minister announced late Friday that President Zine El Abidine Ben Ali had stepped down following violent demonstrations in the capital, Tunis, that have left at least 21 people dead, according to news reports.

Prime Minister Mohammed Ghannouchi said he would be taking over for Ben Ali and a leadership council would rule the country, the reports said. Troops have surrounded the country's main international airport and Tunisian airspace has been closed, according to BBC World Television News.

"Since the president is temporarily unable to exercise his duties, it has been decided that the prime minister will exercise temporarily the duties," the BBC quoted him as saying in an address on state television.

Some news reports said Ben Ali had left the country.

He had dismissed his government and declared a state of emergency following demonstrations in the capital, Tunis, that have left at least 21 dead in clashes with security forces, according to news reports. Human rights groups say at least 66 people have died in clashes this week.

Ben Ali, who ruled Tunisia for the past 23 years, had pledged polls within six months and said he would not stand in another election, but that failed to dissuade Tunisians from taking to the streets on Friday for another day of protests and rioting – the worst that Tunisia has seen in decades. Demands have ranged from more jobs and lower food prices to Ben Ali's departure.

As the death toll mounted on Thursday, Ben Ali ordered security forces to stop using firearms against demonstrators. He also pledged sweeping reforms to increase political and press freedom, as well as reduced food prices.

But protests continued on Friday. The demonstrations erupted in December following the suicide of a university student after police confiscated his produce, saying he was selling it without a permit.