Legal proceedings against Italian premier Silvio Berlusconi, who faces accusations over tax evasion and corruption, have taken a twist because Swiss magistrates are to open formal investigations into four members of the politician’s media empire, the Associated Press said.

The managers are suspected of laundering money linked to overvalued film and TV rights deals in Italy, the news report said.

On 2 September, Swiss prosecutors requested that the Federal Office of Investigating Magistrates open the probe, the report quoted the organisation as saying.

The investigating magistrates could recommend the first Swiss charges in the country's 4-year-old probe of Mediaset and evidence uncovered in Switzerland also could aid Italian prosecutors who are now set to resume tax evasion and corruption cases against Mr Berlusconi.

The Swiss investigation concerns multimillion-dollar money transfers through Swiss bank accounts. These also have been a focus of prosecutors in Milan, whose proceedings against Berlusconi were halted by a 2008 immunity law. A top Italian court overturned that law this week, opening the way for a resumption of legal action.