R Kelly had sexual contact with underage boy as well as girls, prosecutors says.

• Jury selection nears in the sex-trafficking trial of R&B star

• Prosecutors detail new claims but not new charges

Federal prosecutors in R Kelly’s sex trafficking case say the R&B star had sexual contact with an adolescent boy as well as girls, and jurors should hear those claims.

In a court filing on Friday, prosecutors aired a raft of new accusations against Kelly – but not new charges. Jury selection is due to start on 9 August in federal court in New York.

Kelly denies ever abusing anyone. His lawyers did not immediately comment about the additional allegations.

The Grammy-winning singer is charged with leading what prosecutors call a criminal enterprise of managers, bodyguards and other employees who supposedly helped him recruit women and girls for sex and pornography and to exercise control over them.

The charges involve six women and girls, who are not named in court filings.

Prosecutors want jurors to hear about more than a dozen other people the government alleges were sexually or physically abused, threatened, or otherwise misused by Kelly.

Among them, the government says, was a 17-year-old boy, an aspiring musician who Kelly met at a McDonald’s in December 2006 and later invited to his Chicago studio.

After asking the boy what he would do to make it in the music business, Kelly propositioned and had sexual contact with him while he was still underage, according to the court filing.

When Kelly was about to go on trial on child abuse image charges in Chicago in 2008, the same youth told the singer he had access to a juror, prosecutors said, adding that Kelly asked him to contact the juror and vouch he was a “good guy”.

The filing does not say whether the youth did. Kelly was exonerated in that case.

The boy also introduced Kelly to a 16- or 17-year-old male friend, with whom prosecutors say the singer began a sexual relationship several years later. Kelly filmed the two youths in sexual encounters with other people, including some of Kelly’s girlfriends, according to the filing.

Prosecutors say the accounts of the boys and others would help show that the actual charges “were not isolated events and were part of a larger pattern”.

The multiplatinum-selling singer, born Robert Sylvester Kelly, is known for work including the 1996 hit I Believe I Can Fly and the cult classic Trapped in the Closet, a multi-part tale of sexual assignation and conspiracy.

Kelly also faces sex-related charges in Illinois and Minnesota. He has pleaded not guilty.