LOS ANGELES (KTLA) -- In a very public mea culpa, actress Kristin Stewart is apologizing for cheating on her longtime boyfriend -- "Twilight" co-star Robert Pattinson -- with the married director of her most recent movie, "Snow White and the Huntsman."

The admission came after a paparazzo snapped photos of Stewart and British film director Rupert Sanders, 41, kissing on July 17. The pictures were published by US Weekly.

"I'm deeply sorry for the hurt and embarrassment I've caused to those close to me and everyone this has affected," Stewart, 22, said in a statement to People Magazine on Wednesday.

"This momentary indiscretion has jeopardized the most important thing in my life, the person I love and respect the most, Rob. I love him, I love him, I'm so sorry."

News of Stewart's infidelity comes about four years after the couple met while filming the first installment of "Twilight," sparking relationship rumors almost immediately.

Stewart and Pattinson were all smiles as recently as two weeks ago when they appeared together at Comic-Con in San Diego.

For his part, Sanders is married to actress-model Liberty Ross, with whom he has two young children.

He issued his own statement to People on Wednesday, saying: "I am utterly distraught about the pain I have caused my family. My beautiful wife and heavenly children are all I have in this world. I love them with all my heart. I am praying that we can get through this together."

Ross, who appeared as a young Stewart's mother in "Huntsman," tweeted, "Wow," before shutting down her Twitter and Facebook accounts.

A picture of Disney's cartoon Snow White crying and drinking, along with the caption, "Not so pretty or so pure after all..." is posted to an Instagram account that reportedly belongs to Ross.

The final "Twilight" film -- "Breaking Dawn Part 2" -- is scheduled to hit theaters on November 16.