Keri Russell punched Matthew Rhys on The Americans set

Actress Keri Russell shocked her The Americans co-star Matthew Rhys by punching him in the face out of the blue, and now she resorts to violence whenever his mind wanders during filming.

The pair has teamed up to play an onscreen husband and wife in the new action drama, and Russell was required to smack her co-star during a scene for the show's pilot episode.

Under orders of an unidentified director, the actress lashed out at Rhys when he was least expecting it - and now she uses the same trick whenever she needs his attention.

He tells Esquire magazine, "There was a scene where she has to wallop me one. Unbeknown to me, the director whispers to her, 'Clock (punch) him'. We were chatting away, the next thing - whomph, she lands one on me that she must've been preparing the Wednesday before. I've no idea how it went after that.

"Now it's become this running joke on set. She slaps me at moments where she thinks that I'm off guard. I just want that one martial art moment where I catch her, but she's crafty."