After a cryptic posting that was interpreted as a rebuke to those speculating about his private life, Ashton Kutcher has a more forthright message.

The Two and a Half Men star wrote on Twitter: "When u ASSUME to know that which you know nothing of you make an ASS out of U and ME."

His robust comment comes as the 33-year-old actor was seen in public for the first time since rumours began about his marriage to Demi Moore.

He was spotted driving through Los Angeles, presumably after a day on the set of the hit series.

The rumour mill went in to overdrive after Ashton enjoyed a guy's night out on the couple's sixth wedding anniversary.

Demi, 48, hasn't been seen since Monday when she attended a premiere with Jennifer Aniston.

More on Demi and Ashton