The actors met on the set of superhero movie X-Men: First Class in 2010 and speculation was rife that their professional relationship blossomed into romance.

Both have refused to comment on the rumours, with Fassbender recently telling Britain's The Guardian, "My private life is private. If I do a film, how can I expect the audience to follow me if they're thinking, 'He goes out with this person'... It's a disadvantage."

However, they appear to have now gone public with their relationship after they were pictured walking through Manhattan on Sunday (29May11) with their arms around each other.

A source tells Us Weekly, "They're really low-key, but they have a great time together just talking music or movies. They really didn't want to be a topic of conversation during the press for X-Men."