Prosecutors have launched an investigation against Italian Prime Minister Silvio Berlusconi for alleged tax evasion linked to his Mediaset media empire.

The case involves charges of false accounting in the acquisition of television rights by Mediaset.

Prosecutors became involved after a Mediaset-owned firm moved its legal headquarters to the capital, the sources said.

The Italian prime minister rejects investigations into his business dealings, which he says are politically motivated.

Legal proceedings against him have been suspended after his government passed a law giving him immunity from prosecution, pending a ruling from the constitutional court.

Mr Berlusconi and his son, Pier Silvio, are among those being investigators by Roman prosecutors, the sources said.

Mr Berlusconi's lawyer in a statement denied any wrongdoing by either and said the case should be dismissed.

Mr Berlusconi, who accuses magistrates of trying to destroy him politically, is pressing ahead with controversial judicial reforms that are among the key points of contention with former ally turned bitter rival Gianfranco Fini.

Mr Fini's support guarantees the premier a majority in parliament and a potential battle over justice reforms could shatter already fragile government stability.