The trial of Italian Premier Silvio Berlusconi on charges of sex with a minor and abuse of power opened in Milan Wednesday.

Demonstrators hold placard and wear shirts reading "No more" in front of Milan justice court during the first hearing of the "Ruby the Heart Stealer" case's trial on April 6, 2011. Italian Prime Minister Silvio Berlusconi's trial on charges of sex with an underage prostitute, Karima El Mahroug, nicknamed "Ruby the Heart Stealer", and abuse of power, opened and was immediately postponded by judges to May 31. [Xinhua]

Neither Berlusconi nor the minor, dancer and teenage prostitute Karima el Mahrough, best known by her stage name "Ruby", attended the hearing, which lasted less than 10 minutes and was adjourned until May 31.

One of Berlusconi's lawyers, Giorgio Perroni, presented the court with a letter in which the premier said he would like to participate but was unable to because of "institutional commitments".

Security measures were tight around the courthouse in Milan, with about 100 police surrounding the building to prevent riots between groups of supporters and opponents of the premier gathered on a traffic island opposite the building.

More than 100 journalists from around the world requested accreditation for the trial, while TV crews, barred from the hearing, were setting up camp outside the courthouse.

The 74-year-old Italian premier is accused of paying for sex with Moroccan-born el Mahrough from February to May 2010 when she was 17 years old, and then abusing his power in trying to cover it up.

Both Berlusconi and el Mahrough, who is now 18, have denied any wrongdoing in the case.