* Tax fraud trial resumes, followed by "Rubygate" sex case

* Not clear if Berlusconi to attend Wednesday hearing

* PM denies charges, says targeted by biased magistrates

MILAN - Italian Prime Minister Silvio Berlusconi's legal marathon resumes this week with a tax fraud hearing on Monday that will be followed two days later by the long-awaited "Rubygate" trial.

The Ruby case, in which the 74 year-old premier is accused of paying for sex with a teenaged nightclub dancer when she was below the legal age limit of 18, has gripped media attention like few others in recent years.

But it is only one element in a web of legal problems for Berlusconi, one of Italy's richest entrepreneurs as well as its prime minister and dominant political figure.

Over the coming weeks, he faces a series of related trials linked to allegations of fraud, embezzlement and corruption over dealing in television rights by parts of his Mediaset broadcasting empire.

Some of the cases already have opened and Monday's hearing on fraud charges linked to Mediatrade, a unit of Mediaset that deals in broadcast rights, is expected to provide few fireworks, as the prime minister will not be present.

The case centres on accusations that Berlusconi's companies deliberately overpaid for TV and film rights, allowing the difference to be skimmed off by offshore companies run by frontmen and put into illegal slush funds.

Berlusconi, who appeared at a first hearing last week but who will be in Tunisia for talks on the migrant crisis in southern Italy, denies any wrongdoing and says he has been targeted by politically motivated leftwing magistrates.

His opinion poll ratings have suffered but he is in little danger of being forced from office before a verdict which may take years or which may never come.

He has faced at least a dozen trials over the years and has always been cleared or seen the statute of limitations clock run down on the charges he has faced.

Italy's Prime Minister Silvio Berlusconi gestures as he leaves the Justice Palace in Milan March 28, 2011. [Photo/Agencies]

BUNGA BUNGA

The Ruby trial is different from most however, being more graphic and easier for the general public to understand than a complex financial case dealing with offshore front companies and value added tax calculations.

Berlusconi is accused of paying for sex with teenager Karima El Mahroug, (stage name: Ruby) when she was a minor and later making calls to get her released from a Milan police station where she was being held over unrelated accusations of theft.

It is unclear if the premier will appear on Wednesday for the opening day of the trial but he denies doing anything illegal. His supporters say the relentless media coverage over recent months means he has little to fear from new revelations and most to gain from confronting the case head on.

Berlusconi denies ever paying for sex and dismisses the lurid media reports based on prosecutors wiretap evidence of "bunga bunga" sex parties at his palatial private residence outside Milan.

But he faces pressure on a series of other issues.

Italy's economy has been one of the world's slowest growing for the past decade and almost a third of young people are out of work, making stories of teenagers taking home cash-stuffed envelopes from Berlusconi's parties particularly sensitive.

Many in Italy also feel he has been focusing on his legal battles rather than on problems such as the flood of illegal North African migrants into the tiny island of Lampedusa or the perennial garbage scandal in Naples.

While he appears for the moment to have seen off the party revolt that threatened to bring his government down last year, the legal cases and the wider issue of justice reform in Italy look set to overshadow politics for some time.