- The former Italian prime minister is fighting sex charges
- He admits paying witnesses but says he did nothing improper
- Prosecutors accuse him of having illicit sex with "Ruby the Heart-stealer"
- Both Berlusconi and Ruby deny they had sex
Rome (CNN) -- Women who attended "bunga bunga parties" with former Italian Prime Minister Silvio Berlusconi are due take the stand Monday in his trial on charges of having sex with an underage prostitute.
The hearing is the latest in a long-running case around dancer Karima el Mahroug, nicknamed "Ruby the Heart-stealer."
Prosecutors say Berlusconi had sex with her 13 times when she was underage and abused his power as prime minister to get her out of jail when she was held on suspicion of theft.
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Berlusconi's gaffe-tastic moments He denies the charges.
El Mahroug has said that she never had sex with Berlusconi and that she lied to him about her age, telling him she was 24.
Berlusconi acknowledged in an interview over the weekend that he had paid some of the witnesses but said there was nothing improper about the payments.
He said he had given the money to people who had been unfairly hurt because of their association with him.
"All of my guests have had only the fault of having been invited to dinner by the prime minister and have been swept into a colossal media lynching operation," he told the Italian newspaper Il Giornale on Saturday.
"Having the means, when I find myself in front of dramatic and touching cases, I don't hesitate to act, " Berlusconi said.
Ambra Battilana, Chiara Danese and Imane Fadil are due to take the stand on Monday.
Berlusconi resigned as prime minister in November over his country's debt crisis, bringing to an apparent end an 18-year era in which he dominated Italian politics.
