Italian Prime Minister Silvio Berlusconi will remain in hospital at least another two nights after an attack that left him with a broken nose, his doctor said Monday.

Italian press reports meanwhile said his attacker, Massimo Tartaglia, had apologized for what he called a "superficial, cowardly and inconsiderate act."

The 73-year-old prime minister who was hit in the face with a heavy figurine on Sunday is unlikely to leave hospital before Wednesday, Alberto Zangrillo told the ANSA news agency.

"The situation is calm, but (Berlusconi's condition) requires close attention," Zangrillo said, adding that the premier was unlikely to be able to return to work for some 10 days.

Berlusconi was suffering from a severe headache and has difficulty eating, the physician added. His injuries also include a deep cut under his left eye and two broken teeth.

Zangrillo said the prime minister lost half a litre (about 17 fluid ounces) of blood following the assault, which took place after a political rally in Milan, Berlusconi's hometown.

His attacker, Tartaglia, who was arrested immediately after the assault, released a letter through his lawyer late Monday apologising for the attack.

"I don't recognise myself," wrote, 42-year-old Tartaglia, who hurled a heavy replica of Milan's gothic cathedral at Berlusconi.

Tartaglia added that he had "acted alone (with no) form of militancy or political affiliation," the ANSA news agency reported.

The assailant, who has a 10-year history of mental problems, according to Italian media reports, faces up to five years in prison if convicted of having injured Berluconi.

His attack has also raised questions over the competence of Berlusconi's security detail.

It "proves in a worrying way that the system for protecting the head of government is not effective and has gaps in it," said lawmaker Carmelo Briguglio, a member of a parliamentary security panel.

Berlusconi's spokesman Paolo Bonaiuti said the prime minister had recently complained to him: "There's such a spiral of hatred, do you think something might happen?"

Interior Minister Roberto Maroni however said Berlusconi's security detail was "beyond reproach."

World leaders including French President Nicolas Sarkozy, Russian and British prime ministers Vladimir Putin and Gordon Brown, German Chancellor Angela Merkel and Pope Benedict XVI sent messages of sympathy.

US Secretary of State Hillary Clinton voiced her concern in a telephone conversation with her Italian counterpart Franco Frattini.

Berlusconi's first request on Monday was to see the front-page coverage of the attack that newspapers said highlighted political tensions in the country.

Pictures of Berlusconi's bloodied face dominated the Italian press.

The left-wing daily La Repubblica, a fierce political critic of the prime minister, said the attack "highlights the degradation of the political climate in Italy."

"Friends and enemies, partisans and opponents must show solidarity" with Berlusconi. "What is at stake is nothing less than liberty," it said.

Berlusconi is already battling revelations over his private life and divisions within his centre-right coalition.

Leading daily Corriere della Sera said in an editorial there was a "poisoned climate" in Italy.

"Political hate is a monster which when unleashed is difficult to control," it added.

Berlusconi, who began his third stint as prime minister in May 2008, said he would not bow to mounting pressure to go to the polls early.

Allegations about dalliances with younger women led his wife Veronica Lario to file for divorce.

Berlusconi's attendance at the 18th birthday party of aspiring model Noemi Letizia was the last straw for his wife, who is reportedly seeking a settlement of 43 million euros (65 million dollars) a year.

Last week he dismissed accusations of Mafia ties made by a turncoat criminal at an Italian court.

In October Italy's top court quashed an amnesty law that would have benefitted the prime minister, who faces corruption charges. On Friday a Milan court adjourned one of the trials against him until January 15.

The prime minister faces allegations that he paid his British former tax lawyer, David Mills, 600,000 dollars to give false evidence in two trials in the 1990s.