Mila Kunis addressed Justin Timberlake with a "girlfriend bark" as they dined together in London, according to onlookers.

The pair are currently in the UK on the European stretch of their tour promoting comedy Friends with Benefits, where they star as two pals whose relationship becomes physical.

Rumours have been rife that the actors are dating in real life, although Kunis and Timberlake have always insisted they are just friends.

However, as the stars dined at London eatery Nobu with pals last night, onlookers were led to believe they are an item.

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"They were cosying up to each other and she barked at him 'Jay' to follow her. It was like a real girlfriend bark," a source told MailOnline.

"She yelled at Justin across the restaurant in a way that can only mean one thing," added another spy.

One onlooker explained how Kunis and Timberlake were sitting next to one another despite being in a large group, and appeared "cute together". It seems the stars were in the mood to party, as they were seen drinking shots with their friends.

Timberlake split from long-term girlfriend Jessica Biel back in March, with the pair announcing they had ended their relationship amicably.

Kunis also came out of a serious relationship earlier this year, with her publicist confirming she had split from actor Macaulay Culkin back in January.

- AAP