* Protests against government, austerity enter fourth day
* Students clash with police in Rome as ministers speak
* Interior Minister warns of "spiral of rebellion"
* Opposition parties express support for protesters
By Antonella Cinelli
ROME, Dec 12 (Reuters) - Italy's "pitchfork" protests spread to Rome on Thursday when hundreds of students clashed with police and threw firecrackers outside a university where government ministers were attending a conference.
Truckers, small businessmen, the unemployed, students and low-paid workers have staged four days of rallies in cities from Turin in the north to Sicily in the south in the name of the "pitchfork" movement, originally a loosely organised group of farmers from Sicily.
"Our university isn't a catwalk for those who peddle austerity," read a banner at the protest in Rome.
Marches, sit-ins and other protests continued in Milan and Turin, Florence and in the Sicilian capital of Palermo. Larger demonstrations are planned in the capital next week.
"There are millions of us and we are growing by the hour. This government has to go," said Danilo Calvani, a farmer who has emerged as one of the leader of the protests.
Interior Minister Angelino Alfano told parliament the unrest could "lead to a spiral of rebellion against national and European institutions."
The protests are fuelled by falling incomes, unemployment above 12 percent and at a record 41 percent among people below 25, and graft and scandals among politicians widely seen as serving their own rather than the country's interests.
The protesters' precise aims remain vague beyond demanding the government be replaced and parliament dissolved. Targets range from tax collection agency Equitalia and high fuel prices to privileged elites and the euro.
Alfano told lawmakers the government understood "the suffering of poor people," but would not allow the violence to continue. Fourteen policemen have been injured and shops and other property have been damaged in the last few days.
"We intend to defend the freedom of our citizens to live in safety and of our shopkeepers to do business," he said.
He said the government had tried to open talks with the protesters but it was difficult because there were so many different groups and no clear leaders.
While most of the protesters insist they have no political affiliation, several parties, such as the anti-establishment 5-Star Movement and the pro-autonomy Northern League, have offered them support.
Centre-right leader Silvio Berlusconi offered on Wednesday to meet a delegation of truck drivers who are part of the movement before pulling out at the last moment to be replaced by one of his aides.
Mario Borghezio, an outspoken Northern League member of the European Parliament, on Thursday used the protests to attack the euro and European Central Bank chief Mario Draghi.
"The wind of revolt that is blowing in Italy today is the direct result of the euro and the wrong choices made by the EU and the ECB," he said during the ECB chief's testimony to the European Parliament. (Writing by Gavin Jones; Editing by Sonya Hepinstall)