Italy's former prime minister Silvio Berlusconi has been diagnosed with leukemia after he was admitted to hospital, Sky News understands.

The 86-year-old was being treated in intensive care at Milan's San Raffaele Hospital on Wednesday after suffering breathing problems.

A source said the four-time prime minister had been diagnosed with leukemia and is in a stable condition.

"He's stable. He's a rock," Mr Berlusconi's brother Paolo said after visiting him on Wednesday afternoon.

The billionaire media tycoon has suffered several bouts of ill health in recent years, including contracting COVID-19 in 2020.

After being discharged from a 10-day hospital stay, he said the disease had been "insidious" and was the most dangerous challenge he had ever faced.

He has had a pacemaker for years, underwent heart surgery to replace an aortic valve in 2016 and has overcome prostate cancer. He was admitted for a reported urinary tract infection in January 2022.

Mr Berlusconi stepped down as prime minister for the last time in 2011 as Italy came close to a Greece-style debt crisis and he faced several scandals, most notably around his notorious "bunga bunga" parties.

He returned to the Senate after a general election last September.

'Forza Silvio'

Mr Berlusconi's Forza Italia party is part of Prime Minister Giorgia Meloni's right-wing coalition, but he does not have a role in government.

"Sincere and affectionate wishes for a speedy recovery to Silvio Berlusconi," Ms Meloni wrote on social media, adding: "Forza Silvio (Come on Silvio)."