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Days after Mel Gibson's wife of 28 years, Robyn, filed for divorce, a 24-year-old Russian pop singer has come forth, claiming that she had a romantic relationship with the 53-year-old actor and has now fallen in love.

In a new interview in Britain's The Sun, Oksana Pochepa also confirms that she is the mystery brunette photographed kissing Gibson on a Costa Rican beach in March.

"This is serious and I hope that our union will be real and strong and long-lasting," she told the paper Tuesday.

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Us Weekly reports in its latest issue (on newsstands today) that the two met last August when Pochepa was hired to compose a song for Gibson's upcoming thriller Edge of Darkness.

A source on the Massachusetts set tells Us that the pair - who would spend entire days alone together in his trailer - always tried to be discreet about their relationship.

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"They would come out and attempt to walk around separately, but then at the end of the day, they both returned to the same hotel," the on-set source tells Us. "She was there on and off for a week, but it was clear she had no business there other than to be with Mel."

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Fueling more rumors? They met up in January in Mexico City, where Gibson directed a music video for Pochepa.

"Mel's team brought all of their own people," Alejandro Alvarez of Estudios Churubusco tells Us of the shoot.

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For more on Gibson's shocking divorce - including what Robyn stands to get out of his $900 million fortune and how his controversial 2006 DUI arrest was the "final straw" for her - pick up the new issue of Us Weekly today!