"Government in danger," said Il Messaggero daily, while Il Fatto Quotidiano said the uneasy alliance between Berlusconi's centre-right and Prime Minister Enrico Letta's centre-left was "a dead man walking".
Although Berlusconi loyalists had threatened mass resignations if the ruling went against him, they have been more cautious following the verdict.
"Silvio Berlusconi's legal woes will not be a problem for the government," said Mara Carfagna from Berlusconi's People of Freedom party.
"This anger we all feel must not boil over," she said.
The Milan stock market opened 0.14 percent higher and the difference between Italian and German 10-year sovereign bonds – a key measure of
investor risk – narrowed to 266 points from 269 points on Thursday.
Shares in Berlusconi's business empire Mediaset, however, fell over 4.0 percent at the start of trading.
The greater uncertainty is whether Letta will manage to contain growing discontent within his own Democratic Party about governing together with a coalition led by a confirmed tax fraudster.
Pippo Civati, a prominent party member, told La Repubblica daily that the government needed an "exit strategy" and that fresh elections should be held "within the next few months, not in two years".
Some leftists have also called for the 76-year-old Berlusconi to be expelled from his seat in the Senate as soon as possible in line with new rules against lawmakers and candidates with criminal records.
The country's highest court on Thursday handed the billionaire tycoon his first definitive conviction in a 20-year political career that has been dogged by legal woes and sex scandals.
The court ordered the three-time former prime minister to do a year of community service or be placed under house arrest once his parliamentary immunity is lifted — an unprecedented verdict for Italy.
The supreme court also said an appeals court should rule on whether he should be temporarily banned from public office, a decision that would eject Berlusconi from parliament for the first time since 1994.
An embittered and visibly shaken Berlusconi delivered a video message on Italian television late on Thursday in which he dismissed the sentence as baseless and vowed to continue his political career.
"For the commitment I have shown these past 20 years for my country and as I reach the end of my active life, I have been rewarded with accusations and a sentence based on nothing at all," Berlusconi said.
"This is a country that does not know how to be just," he said, speaking from his luxury residence in Rome, adding that the sentence "takes away my personal freedom and political rights".
The conditions of Berlusconi's sentence are to be determined but he will need judicial permission to carry out political activities and is excluded from running for office for the next six years.
In any case the Senate will have to vote to lift Berlusconi's immunity before the sentence can be implemented — a process that could take weeks or even months depending on the political situation.
Berlusconi's lawyers, who have repeatedly condemned the legal attacks against him as politically motivated, said they were weighing a possible appeal at the European Court of Human Rights.
Letta also on Thursday called for calm "for the good of the country" as he struggles to lead Italy, the eurozone's third largest economy, out of its worst post-war recession.
The current government was installed following a two-month deadlock between Berlusconi and the Democratic Party after close-run February elections.
The case against Berlusconi revolved around the purchase of film distribution rights by Mediaset – the platform for his first entry into politics.
Berlusconi is still appealing convictions in other cases for having sex with an underage prostitute, abusing his prime ministerial powers and leaking
a police wiretap to damage a political rival.
Prosecutors have also filed charges alleging that he bribed a senator to join his ranks in a move that helped bring down the government in 2008.
All other fraud and bribery charges against him over the years have either been overturned on appeal or have expired under the statute of limitations thanks to Italy's slow-moving justice system.