JERUSALEM (AFP) - Israeli Energy Minister Silvan Shalom, tipped as a possible presidential candidate, was questioned by the police on Tuesday over what media said were suspicions of a 1999 sexual offence.

"He was questioned for two hours by the national unit of the Israeli police which deals with cases involving officials," police spokesman Micky Rosenfeld told AFP.

Without specifying the nature of the allegations, Mr Rosenfeld said they were related to "an old case that took place more than 15 years, and he gave his version".

Since Monday, the media have been reporting that Mr Shalom has been accused of sexual assault by a former female employee.

The reports say the woman has filed a complaint against Mr Shalom, a member of Prime Minister Benjamin Netanyahu's Likud party.

Speaking anonymously, she told army radio that, in 1999, then science minister Shalom had called her to deliver documents to a Jerusalem hotel room where he was staying and that she had found him naked.

She said Mr Shalom then forced her to perform oral sex on him.

Mr Shalom, now 55, has been expected to run in a June 14 presidential election to succeed Shimon Peres, and was about to announce his candidature, according to local media.

He appears to be immune from prosecution under an Israeli statute of limitations, since the incident dates back more than 10 years.

But the police are keeping the investigation open, as more women are coming forward with similar accusations, army radio said.

Ms Gila Gamliel, a Likud MP close to Mr Shalom, told the radio the minister's entourage "rejected" the allegations, suggesting they were part of a smear campaign ahead of the presidential election.

Former president Moshe Katsav began a seven-year jail sentence in December 2011 after being convicted on two counts of rape and other sexual offences.