Justin Timberlake cheating on Jessica Biel with Rihanna?

Justin Timberlake is rumoured to be hooking up with Rihanna in New York behind girlfriend Jessica Biel's back.

The singer, who teamed up with the R&B lady on her third album, 'Good Girl Gone Bad', may soon dump Jessica, insiders claimed.

"Justin and Rihanna have been seeing each other for the past few weeks," the Herald Sun quoted a source close to Rihanna as telling Showbiz Spy.

"He is really into her and it's only a matter of time before he dumps Jessica," the source added.

The pair was also alleged to be the recent New York Daily News blind item about a female star giving a male singer a "private" lapdance.

The source said: "That blind item about which two pop stars made sweet music together, the girl giving the guy a lapdance is Rihanna and JT!

"It was at 10am in NYC and they left together. They are seeing each other on the low!"