ROME (AFP) - Italy's top court on Tuesday confirmed the acquittal of Silvio Berlusconi on charges that he paid for sex with an underage dancer and then abused his position as prime minister to cover it up.

After nine hours of deliberations, the judges at the Court of Cassation delivered a ruling that brings to an end a lengthy legal saga centred on the billionaire media tycoon's infamous "bunga bunga" sex parties.

It also leaves the 78-year-old free to resume a central role in Italian politics.

Berlusconi has just finished serving a community service order for tax fraud and remains embroiled in several other legal cases. But they are thought unlikely to prevent him from returning to politics and spearheading opposition to Prime Minister Matteo Renzi's plans to transform the way Italy is governed.

Tuesday's late-night verdict came after a hearing in which a senior prosecutor had described the elderly party-lover as having a "dragon's passion" for teenage girls.

Berlusconi was convicted in 2013 of the most serious charges he has faced in a scandal-tainted career, only to be acquitted on appeal a year later.

The quashing of his seven-year prison term and a lifetime ban from public office triggered a counter-appeal by prosecutors to the Court of Cassation.

After a 31/2-hour hearing earlier on Tuesday, the judges spent nine hours considering their eagerly awaited verdict.

The billionaire businessman whose empire includes the AC Milan soccer club, has always denied paying for sex with a 17-year-old dancer called Karima El-Mahroug who went by the stage name "Ruby the heart stealer".

He maintained he only tried to help the Moroccan national when she was later arrested for an alleged theft because he thought she was a niece of the then Egyptian president Hosni Mubarak.

The appeal court appeared to accept that argument when it ruled that Berlusconi had not abused his power. The court also ruled that Berlusconi had not committed a crime in having sex with Ruby as he did not know she was under 18, the legal minimum for a prostitute to sell sex in Italy.