Tunisian PM Mohamed Ghannouchi pledges to quit politics
Tunisia's prime minister has promised to leave politics after elections being planned in the wake of President Zine al-Abidine Ben Ali's fall last week.
In a TV interview on Friday, Mohamed Ghannouchi said he would quit "in the shortest possible timeframe".
His interim government has promised to hold polls within six months, but it has so far not set a date.
On Saturday, thousands of protesters, including police, took to the streets of Tunis to demand the cabinet resign.
The BBC's Magdi Abdelhadi, in the Tunisian capital, says the police participation was a very dramatic development - until a week ago they were defending the now-ousted government of Mr Ben Ali.
The officers insisted that they had not been to blame for the deaths of dozens of protesters since mid-December, with many chanting: "We are innocent of the blood of the martyrs!"
They also called for the creation of a police union and better pay.
Later, Tunisians held a candlelit vigil to mark the second of three days of mourning for those killed during the uprising that prompted Mr Ben Ali and his family to flee to Saudi Arabia on 14 January.
Ministers in the interim government are reported to have been meeting in a special closed-session on Saturday to discuss how to restore calm.
Prime Minister Ghannouchi, who was a key ally of the ousted president, made an emotional plea for patience on television on Friday.
He said he would retire from public life after the elections, and promised that all "anti-democratic laws" would be repealed by the transition cabinet.
"I lived like Tunisians and I feared like Tunisians," he said. "I pledge to stop all my political activity after my period leading the transitional government."
At least 78 people have been killed since a wave of protests began last December, although the UN estimates that the death toll has exceeded 100.
Three days of mourning began on Friday. Flags were lowered, and at the Quds mosque in Tunis, an imam prayed for the dead and for democracy, the Reuters news agency reported.
At Friday prayers, there was none of the heavy security around mosques seen under Mr Ben Ali's rule, nor the customary mentions of the former president by imams.
Mr Ghannouchi has left Mr Ben Ali's ruling Democratic Constitutional Rally (RCD) party and insisted that members of the interim government who served in the previous administration - including the ministers of defence, interior, finance and foreign affairs - have "clean hands".
But the country's main trade union, the General Tunisian Workers' Union (UGTT), has called for a new administration with no links with the ousted regime.
The UGTT's deputy head, Abid Briki, told the AFP news agency that such a "national salvation government" was "in accordance with the demands of the street and political parties".
A protest march backed by the UGTT, called the "Caravan of Liberation", set off from central Tunisia for the capital on Saturday, reaching the town of Regueb by nightfall.
"The aim of this caravan is to make the government fall," Rabia Slimane, a teacher in Menzel Bouzaiane - the town where the first victim of the uprising was killed by security forces in December - told AFP.
Opposition CPR party leader Moncef Marzouki, who returned to Tunisia on Tuesday after two decades of exile in Paris, said Prime Minister Ghannouchi was a "factor of instability".
"A prime minister who served more than 10 years in a dictatorship isn't able to build a democracy," he said.
"Tunisia is at a crossroads, and needs stability, a return of confidence and hope," he added. "This is a delicate phase."
The government has faced continuing protests against figures from the previous regime remaining in positions of power.
Four opposition ministers quit over the issue, just one day after the cabinet was formed.
The interim cabinet has promised to release all political prisoners and said previously banned political groups will now be legal.
It has also announced that 33 members of Mr Ben Ali's family have been arrested.
According to Interior Minister Ahmed Friia, one of those was Imed Trabelsi, a nephew of Mr Ben Ali's wife, who was previously reported to have been stabbed to death.
Mr Ghannouchi also said on Friday that Tunisia would pay compensation to victims of abuse during Mr Ben Ali's rule, Reuters reported.
Mr Ben Ali fled to Saudi Arabia following a wave of demonstrations attributed to economic grievances and resentment about a lack of political freedom.
His extended family was widely despised because of its conspicuous consumption and perceived corruption.
The protests against his rule began after a man set himself on fire in central Tunisia on 17 December.