Demi Moore has filed for divorce from Ashton Kutcher after six years of marriage.

The actress, 49, announced the news in a statement yesterday (18 November), saying it was with "great sadness and a heavy heart" that she had decided to end the relationship.

The move follows months of speculation that the couple's marriage was on the rocks, after allegations of Ashton's infidelity surfaced in September.

"It is with great sadness and a heavy heart that I have decided to end my six-year marriage to Ashton," Demi said, in a statement released via her publicist.

"As a woman, a mother and a wife there are certain values and vows that I hold sacred, and it is in this spirit that I have chosen to move forward with my life."

"This is a trying time for me and my family, and so I would ask for the same compassion and privacy that you would give to anyone going through a similar situation."

Minutes later Ashton, 33, responded on Twitter. "I will forever cherish the time I spent with Demi," he said. "Marriage is one of the most difficult things in the world and unfortunately sometimes they fail."

Demi and Ashton began dating in 2003. They wed two years later, in a secret ceremony in Beverly Hills. Ashton became stepfather to Demi's tree daughters - Rumer, Scout and Tallulah Belle - from her previous marriage to Bruce Willis .

Their relationship fell under scrutiny earlier this year, after socialite Sara Leal, 22, claimed she had an affair with Ashton on his and Demi's sixth anniversary. This followed a previous allegation that the Punk'd star had been unfaithful in 2010.

Ashton's spokesperson denied the allegation but the couple were said to be experiencing difficulties and turned to their Kabbalah instructor to work through their issues.

No divorce papers have been filed yet in Los Angeles Superior Court, according to a number of reports.

Click here to look back on Demi and Ashton's relationship in photos.

Demi & Ashton to divorce