ROME (AFP) - Silvio Berlusconi's acquittal of paying for underage sex leaves him a free man, but can the former premier claw back his political power and return to the top?

The media magnate was celebrating Wednesday after Italy's top court quashed once and for all accusations that he had paid for sex with a starlet nicknamed "Ruby the Heart Stealer" at his infamous "bunga bunga" sex parties.

"Finally the truth. Today is a beautiful day for politics, justice, the rule of law," Berlusconi, 78, said in a statement, adding: "I am back in the field, to build... an Italy that is better, freer and fairer."

The former premier's lawyer Franco Coppi had told the court that while "not even the defence team is denying acts of prostitution took place" at Berlusconi's raunchy dinner parties and hot-tub sessions, it was all above board.

The judges said there was no proof the self-proclaimed Latin lover knew the buxom dancer was just 17 at the time.

While the magnate's devotees exulted, his victory sparked no little satire on social networks, with one Twitter user saying "after Berlusconi's acquittal, the wolf accused of having eaten Little Red Riding Hood's grandma is let go."

"I naturally thank the judges who did their duty without being influenced by media pressures," the ex-premier said, contradicting his previous claims he was being persecuted by left-wing magistrates.

'ALWAYS ABLE TO SURPRISE'

Some commentators said the billionaire would now be gearing up for general elections expected to be held in 2018, but analysts cast doubt on his chances of resuming a heavyweight role in Italian politics.

"Berlusconi is still Berlusconi, and is always able to surprise," Franco Pavoncello, professor of political science at Rome's John Cabot University, told AFP.

"From a legal point of view he is free to take to the field again, but what remains to be seen is whether he has the physical strength. The years are passing and he is giving signs of slowing down," he said.

Berlusconi has just wound up a community service order for tax fraud and still faces accusations of bribing a senator for political gains and paying off witnesses in the Ruby case.

These are thought unlikely to prevent him from trying to spearhead opposition to Prime Minister Matteo Renzi's reform plans, though his centre-right Forza Italia is fragmented and he faces leadership challenges.

Rising star Matteo Salvini, 42, head of the anti-immigration Northern League party, has an eye on Berlusconi's throne.

"Salvini has nothing to fear from a man who is, by now, on his political deathbed," said Marco Tarchi, political science professor at Florence University. Polls put Salvini well ahead of Berlusconi in terms of popularity.

"Berlusconi's time is up, even if he and his allies refuse to realise it," Tarchi added.

He may pick some fights with Renzi, particularly with regional elections looming in May, but the media magnate is unlikely to want to unseat the government and spark early elections.

'PROSTITUTES BLACKMAIL THREAT?'

His tax fraud sentence saw him banned from public office for two years starting in 2014.

He is also subject to a 2012 law banning convicted MPs from running for office for six years, which Berlusconi is appealing in the European Court of Human Rights.

Political observers at Il Sole 24 Ore daily said getting the law changed would now be top of the tycoon's to-do list.

In any case, three years after completing his tax sentence Berlusconi will be able to request his slate be wiped clean, Italian media reports say, in which case he could run, in 2018, for a fourth stint as prime minister.

But Giacomo Marramao, of Roma Tre University, says the AC Milan football club owner is more worried about protecting his business interests - and in any case has undermined his chances of a return by bedding prostitutes.

"He has lost the trust of the Italian electorate, not by having lovers but having indiscriminate relations with prostitutes which leave him vulnerable to blackmail," he said.

"Who knows how many of these women have been privy to inside details of Italian or international politics?" Marramao said.

Berlusconi "may be ready to fight a few battles" but from now on he is likely to be little more than "an elderly father" to the right, the academic added.