“State of Affairs” star Katherine Heigl’s “intense” friendship with on-screen squeeze Chris McKenna is generating hot gossip in Tinseltown!

The married mom of two and hunky Chris have been steaming up the NBC show’s set with their love scenes, sources said. “They look like they’re REALLY enjoying their sex scenes a lot,” blabbed an inside source.

Another show insider said: “Chris is a total flirt and it’s like she’s completely in awe of him. He even makes her giggle and blush! They’ve formed an intense bond on set.”

Insiders fear Chris, 37, is a “player” and that this could end up with him and his leading lady in the sack.

Meanwhile, pals of the 36-year-old actress said her hubby, singer-songwriter Josh Kelley, should keep a close eye on her flirty co-star, who’s dated and dropped several sexy cuties.

“I think Chris is exciting to Katherine because he’s so different from Josh, both physically and in personality,” said the source.

Chris also stars as detective Mark Harding on the daytime soap, “The Young and The Restless.”

Meanwhile, producers hired Chris to inject sex appeal into “State of Affairs,” said the source, but now believe their move could backfire if the on-set chemistry with Katherine becomes more!

“He sees her as nothing more than a notch in his belt. The bosses are worried that it could all end in tears and hurt the series,” claimed the source.

As it is, Katherine is battling to restore her reputation after her diva behavior on TV’s “Grey’s Anatomy,” and several box office bombs.

“Any romance with Chris could be a dangerous game,” a set insider explained.

“He has no intention of settling down with anyone, let alone a woman with two kids.”