Italian former prime minister Silvio Berlusconi, who has been in hospital for leukaemia and a lung infection, is getting progressively better, doctors said Monday, expressing "cautious optimism" over his condition.

Berlusconi, a billionaire and larger-than-life figure in Italian politics, has been in intensive care at Milan's San Raffaele Hospital since Wednesday.

"The last 48 hours have seen a progressive and steady improvement in monitored organ function," his doctors said in a bulletin Monday. 

Treatment was producing "the expected results, allowing us to express cautious optimism". 

He remains in the intensive care unit, they said. 

Doctors revealed Thursday that Berlusconi was being treated for a lung infection and was suffering from chronic myelomonocytic leukaemia (CMML), a rare type of blood cancer affecting mainly older adults.

The three-time premier -- who currently serves as a senator and leader of the Forza Italia far-right party -- has been in declining health in recent years, marked by frequent hospital stays. He is rarely seen in public.

His latest hospital admission came just a week after being discharged after a four-day stay.

Called "the immortal" for his longevity in politics, the self-made media mogul elicits either fervid admiration or disdain from Italians, his many business and political successes having gone hand-in-hand with decades-long legal battles. 

In September 2020, Berlusconi was in hospital for 11 days for Covid-related pneumonia, complications from which caused a series of hospital stays during 2021. 

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

Forza Italia is a junior member of Prime Minister Giorgia Meloni's right-wing coalition government.