Rome: Italian former prime minister Silvio Berlusconi, dubbed "the immortal" for his longevity in politics, was "stable" Thursday after a night in intensive care but has reportedly been diagnosed with leukaemia.

The 86-year-old media mogul and senator, who has been in and out of hospital in recent years, was admitted Wednesday to the cardiac unit at Milan's San Raffaele Hospital after suffering respiratory problems.

"We're all very worried," Deputy Culture Minister Vittorio Sgarbi, Berlusconi's close friend, said Thursday.

"I hope he has the strength in him to resist this latest attack, which now has a sinister name, leukaemia."

Italy's best-selling Corriere della Sera daily also said the magnate has been diagnosed with leukaemia.

Berlusconi's spokesman Paolo Russo said he was not authorised to give health information, but "the Corriere della Sera is the most authoritative Italian newspaper".

The magnate -- a controversial, larger-than-life figure who elicits either admiration or disdain from Italians -- began chemotherapy on Wednesday, according to ANSA news agency, which cited sources close to the ex-prime minister.

As close family members arrived at the hospital, Foreign Minister Antonio Tajani said he had spoken to Berlusconi's doctor, who told him "his condition is stable".

He also said Berlusconi was feeling well enough to be making phone calls.

- 'The country I love' -

The billionaire leader of the right-wing Forza Italia party spent four days last month at the same hospital for what Italian news reports called heart issues, before being discharged last Thursday.

"I have already started working again... ready and determined to commit myself, as I have always done, to the country I love," he said in a message posted on social networks Friday.

And on Sunday, he posted a photo of himself grinning in front of a vast lawn of tulips in his villa in Arcore, in northern Italy.

After dominating Italian politics for decades, the "Cavaliere" -- as he is widely known in Italy -- now appears physically diminished on the rare occasions he is seen in public.

Long gone are the days of his infamous erotic "bunga bunga" parties with young starlets, which he has always insisted were nothing more than elegant dinners.

Forza Italia is a member of Prime Minister Giorgia Meloni's right-wing coalition government, although the party attracts only about 10 percent of voters.

Meloni tweeted her "sincere and affectionate wish for a speedy recovery" Wednesday, while Matteo Salvini, whose League party is also a coalition member, tweeted "Forza Silvio, Italy is waiting for you!"

Berlusconi was in hospital for 11 days for Covid-related pneumonia in September 2020, after contracting the virus while on holiday in Sardinia. He described it as "perhaps the most difficult ordeal of my life".

The following year, Covid-related complications caused a series of hospital stays.

The one-time cruise ship crooner had open heart surgery in 2016 and surgery on his intestine three years later.

Berlusconi served as prime minister three times after entering politics in 1994, and for millions of Italians he represented a golden age of the Italian economy and the self-made man.

Despite a series of sex scandals and court cases which threatened to tarnish his image -- including being convicted for tax evasion in 2012 -- he has held a soft spot in many Italians' hearts since then.