Tunisia said Wednesday it had issued an international arrest warrant for ousted president Zine El Abidine Ben Ali, who resigned this month amid protests against his regime and fled to Saudi Arabia.
The justice ministry said Ben Ali, his wife Leila Trabelsi and other members of his once all-powerful family were accused of illegally acquiring assets and transferring funds abroad during the veteran leader's 23-year regime.
The announcement came as tensions mounted in the north African state ahead of a critical cabinet shake-up expected to be announced on Wednesday, amid clashes in Tunis at a protest calling for a clean break with the old regime.
Riot police tear-gassed protesters who have been rallying in the main government quarter in Tunis for four days after some of them tried to force a barrier, while security forces sealed off the area with barbed wire.
An AFP reporter saw some 200 protesters throwing stones at police.
Protesters are calling for figures linked to Ben Ali's regime to be removed from the new government and for his powerful RCD party to be disbanded.
US President Barack Obama said in a speech on Tuesday that in Tunisia "the will of the people proved more powerful than the writ of a dictator."
"And tonight, let us be clear: the United States of America stands with the people of Tunisia, and supports the democratic aspirations of all people."
His comments came after thousands took to the streets in Egypt to call for an uprising against President Hosni Mubarak similar to the one in Tunisia.
Four people were killed during the rallies, which were the biggest since riots over bread subsidies shook the Arab world's most populous nation in 1977.
An Egyptian opposition group called for a second day of protests on Wednesday, while the interior ministry said any further rallies were banned.
Assistant Secretary of State Jeffrey Feltman, the top-ranking US official on the Middle East, meanwhile visited Tunis to press for democratic elections.
Other Arab states should tackle reforms after Tunisia's "example", he said.
"I think there's real potential now for a much warmer, mutually beneficial US-Tunisian relationship that will emerge particularly after democratic elections," he told reporters on Tuesday after talks with four ministers.
Hundreds and sometimes thousands of protesters in Tunis have kept up daily and mostly peaceful protests against the government since last week.
"Down with the government," the protesters chanted at the rally on Wednesday, which has defied a curfew and a ban on public assemblies.
Bassem El Barouni, a young man in the crowd, said: "We have only one demand. For the government to fall. They all have to go.
"(Prime Minister Mohammed) Ghannouchi should go first."
The main UGTT trade union, which has led opposition to the new government, said a general strike was also under way in Tunisia's second city, Sfax.
Many of the protesters in Tunis arrived Sunday from impoverished regions in central Tunisia where social demonstrations against Ben Ali began last month.
The government has announced economic aid for the regions and compensation for the families of the dozens of people killed by Ben Ali's security forces.
There were also increasing signs of exasperation among many Tunisians over the chaotic upheaval that has followed in the wake of Ben Ali's downfall.
There have been protests in favour of the government and calls for a return to normal economic activity in various parts of the north African state.
Many schools and universities have remained shut despite orders to re-open.
The offices of the UGTT, the General Union of Tunisian Workers, have also been attacked in the cities of Beja, Gafsa, Kasserine, Mehdia and Monastir.
Tunisia has announced unprecedented democratic freedoms but Ghannouchi, who has been prime minister since 1999, has said he will stay on until elections.
The government has said 78 people were killed during the anti-Ben Ali protests; on Wednesday it said that 71 prisoners also died in recent riots.