The apology came after pictures appeared in US Weekly magazine of the 22-year-old Twilight actress together with 41-year-old Saunders, who directed her latest movie Snow White and the Huntsman.

"I'm deeply sorry for the hurt and embarrassment I've caused to those close to me and everyone this has affected,” Kristen wrote in a statement to People magazine.

"This momentary indiscretion has jeopardised 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."

Meanwhile, Sanders, who has two young children with his model wife Liberty Ross, has also issued a statement.

"I am utterly distraught about the pain I have caused my family,” he wrote in a statement to People magazine.

"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.”

The photographer who took the pictures of the pair, which shows them with their arms around each other (see them in the video below), said the pair looked like they were very involved with each other.

"He was all over her. (They) would only take a break when they thought someone was walking by. It seemed like they couldn't get enough,” the photographer said.

Stewart, who took time out from promoting the Twilight series to focus on the new $170 million movie, has been seen promoting the film alongside Ross who played Queen Eleanor in the movie.

The 44-year-old actress alluded to the heart-breaking affair through a series of tweets writing: "WOW" and quoting Marilyn Monroe, writing: "Good things fall apart so better things can fall together".

Stewart and Pattinson were last seen together at the Teen Choice Awards just days before news broke of the affair. Pattinson is yet to comment on the events publicly.

The pair seems set for an awkward reunion come November as they share promotional commitments to the final instalment of the Twilight series, The Twilight Saga: Breaking Dawn − Part 2.