LOVE-STRUCK STARS MCCORD, LUTZ LET IT ALL OUT

[Renesbella]

by nypost.com "TWILIGHT" star Kellan Lutz and "90210" actress AnnaLynne McCord don't want the press to know they're an item, but the comely young duo didn't mind letting guests find out at Social Life magazine's Fourth of July bash in Water Mill.

Lutz -- who graces the July issue of the glossy with heiress Lydia Hearst -- refused to pose for photos with McCord while at the holiday celebration, despite the fact that McCord had been loaned $300,000 worth of Kwiat diamonds to wear specifically for the occasion.

But a source tells Page Six that Lutz wasn't shy about showing his affection for her in private. Our spy laughed, "At one point, they went into a room upstairs arm in arm and Lutz jokingly announced to the people hanging out inside, 'We're looking for a place to [bleep].' Someone directed them to a bathroom, and they went in."

The couple also partied together later at the Axe Body Spray lounge in Southampton and then kept their togetherness going at the Montauk Yacht Club.

Also at Social Life's party were "Real Housewives of New York City" star Kelly Bensimon, Minnie Mortimer, her husband, "Traffic" director Stephen Gaghan, songwriter Jamie Jo Harris, and "Terminator" star Nick Stahl, who, we're told, ended up sleeping in the pantry.

Although she was on the cover of the magazine and had committed to hosting the Independence Day party, Hearst herself unfortunately didn't make it. The madcap heiress called the event's organizers to say she was in a hospital emergency room with kidney stones.

A rep for Hearst yesterday said, "She's actually back on set for a photo shoot. She's feeling much better."