Rihanna and Ashton Kutcher's "friendship" will lead to something romantic, it has been claimed.

Speculation over the nature of their relationship has been rife since Rihanna was photographed leaving Ashton's Hollywood home last week.

Although the pair have denied they are involved, those close to them believe it is only a matter of time before they become a couple.

"They are both young, free and single. It's undeniable they have chemistry," a source told UK magazine Grazia.

"Everyone's expecting to see them out together again soon."

Sources also claim Ashton, 34, has been chasing the 24-year-old Barbadian singer for months. Ashton reportedly reached out to Rihanna when he heard she was looking to buy a new place in Los Angeles.

"Of course Ashton fancies Rihanna is there any man who doesn't," an insider said.

"He's been after her for months, and when he heard she was looking to buy a new place in LA, he got in touch. Despite moving in the same circles, they've never really had all that much to do with each other, until now. Everyone's convinced that if something didn't happen that night, it's only a matter of time before it does."

The news of their alleged romance is said to have upset Ashton's estranged wife Demi Moore. Demi has been keeping a low profile since she left rehab reportedly for various addictions. "She is constantly keeping tabs on Ashton on the internet, so when these pictures came up she was understandably devastated," a source said, adding "she felt sick to her stomach" over reports they were an item.