Gerard Butler recently got very touchy-feely with his The Bounty Hunter costar Jen Aniston -- and there's photographic proof.
In a buzzed-about rearview photo from March 27, Butler tightly grabbed Aniston's bottom while greeting fans on the River Seine in Paris.
During a Friday appearance on syndicated radio show "Johnjay and Rich," Butler, 40, joked about the bootylicious snapshot.
"I'm a bit of a bad boy," the actor said. He then demurred, "by the way, I'm still not sure my hand was really on her butt. I think that's just the way the camera was angled," before breaking into laughter. "I actually haven't seen [the photo]."
His interviewers weren't buying it. "[Your finger] looks implanted inside the crease!" one co-host protested.
The star also continued to deny any romantic involvement with Aniston, 41. "If I was going out with Jennifer, I'd be more than happy to say I'm going out with Jennifer -- it's just not true."
Yet a Butler pal counters in the new Us Weekly that the flirty costars have been "hooking up for a while." Another source confirms that the pair slept together during her February birthday blowout in Mexico.
An Aniston pal explains: "she'd like it to be more, [but] they're friends with benefits."
A rep for Aniston tells Us that the "friends with benefits" label is "crude and incorrect. They were not flirty in Paris."