Mila Kunis and Ashton Kutcher are rumoured to have got engaged.

The couple are believed to be planning to get married and Mila has been spotted wearing a diamond engagement ring, according to E!.

A source told E! that the pair are planning to make things official after Mila was seen with the ring while out shopping.

The pair have yet to comment on the rumours, but Mila posted a photo of her with Ashton on Instagram, with the caption: "I love you @kutcher78."

Mila and Ashton first met when they were co-stars on That '70s Show from 1998 to 2006 and have been dating for nearly two years.

Ashton was previously married to Demi Moore, but split from her around seven months before getting together with Mila, who at first laughed off rumours of the romance, calling them "absurd".

When they first got together, their former sitcom co-star Kurtwood Smith said: "It's amazing. They're both great people, so I'm happy for them. Maybe they should get married. We'll all go to the wedding and that could be the reunion. It'll be a reality show."