Demi Moore and Ashton Kutcher split

Demi Moore and Ashton Kutcher in happier times

Demi Moore has announced "with great sadness" the end of her six-year marriage to fellow actor Ashton Kutcher.

The Hollywood power couple's split follows reports in recent months of Kutcher's alleged infidelity.

Kutcher tweeted that he would "forever cherish" his time with Moore.

Moore, 49, and Kutcher, 33, were wed in September 2005. She had previously been married to actor Bruce Willis for 13 years.

No divorce papers had been filed in Los Angeles Superior Court as of Thursday afternoon, reports the Associated Press news agency.

'Trying time'

Moore made no immediate comment on her Twitter feed - her usual method of sharing news - instead releasing a statement via her publicist.

"It is with great sadness and a heavy heart that I have decided to end my six-year marriage to Ashton," it said.

"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."

Kutcher, who recently took over from Charlie Sheen in the hit TV series Two and a Half Men, tweeted minutes later: "I will forever cherish the time I spent with Demi. Marriage is one of the most difficult things in the world and unfortunately sometimes they fail. Love and Light, AK."

Kutcher became a stepfather to Moore's three daughters - Rumer, Scout and Tallulah Belle - from her marriage to Willis.

Moore and Willis divorced in 2000, but remained friendly.

Her acting credits include Ghost (1990), A Few Good Men (1992) and Indecent Proposal (1993).