Italy's President Giorgio Napolitano is starting a series of meetings with senior politicians to try to agree on a new caretaker government after Prime Minister Silvio Berlusconi resigned on Saturday.
It is hoped the new government will be named before the world's financial markets reopen on Monday.
The President is expected to ask former European Commissioner Mario Monti to take the top job.
Mr Berlusconi, who dominated the country's politics for 17 years, faced a chorus of jeers and insults as he was driven to the Quirinale Palace to hand in his resignation.
Police struggled to deal with the large, hostile crowd and Mr Berlusconi left by a side exit to avoid the protesters.
He submitted his resignation to the President after the lower house of parliament passed a package of austerity measures to restore confidence in the country's economy.
Members of the lower house voted 380-26 with two abstentions, after the Senate approved the measures on Friday. President Napolitano later signed the bill.
Mr Berlusconi, who lost his parliamentary majority in a vote on Tuesday, promised to resign after the austerity measures were passed by both houses of parliament.
Mr Berlusconi, 75, created his own party in 1993 to fill a void on the right caused by the destruction of the Christian Democrats by a corruption scandal.
He won three elections in 1994, 2001 and 2008 and was Italy's longest-serving prime minister since World War II.
Mr Berlusconi once described himself as the best head of government since Italy was created nearly 150 years ago.
But his premiership was recently marred by many scandals.
The BBC reports he has been the object of at least 23 judicial investigations, mostly for corruption. He is currently involved in several trials for fraud, corruption and under-age sex.
He is still the single richest man in Italy.