London, Apr 14 : Mel Gibson's wife has filed a divorce petition weeks after the actor was spotted frolicking with a brunette on a beach.

Robyn Gibson, 52, has filed papers to end their 28 years of marriage citing "irreconcilable differences".

Sources blame the split on Mel's relationship with a Russian musician called Oksana.

The pair had reportedly become close on the set of his latest film The Edge of Darkness, and were snapped coming out of his trailer together, however, the Oscar winner denies any affair.

The Lethal Weapon star is worth up to 640 million pounds and Robyn will be entitled to half the actor's earnings during their 28-year marriage, reports the Sun.

Mel also owns a 28-million pound church in Malibu and a 10-million pound island in Fiji.

While Robyn has listed their separation date as "to be confirmed", Mel has given an exact separation date of August 26, 2006 - less than a month after his infamous DUI arrest.

The couple has seven kids.

In her papers, Robyn has asked for a joint custody of Tom, their younger child as well as spousal support and legal fees.

Mel and Robyn released a statement yesterday, saying: "Throughout our marriage and separation we have always strived to maintain the privacy and integrity of our family and will continue to do so." (ANI)