Liam Hemsworth was reportedly involved in a street fight in the early hours of Sunday morning (9 December).
The Hunger Games actor - who is engaged to Miley Cyrus - was involved in an altercation outside a bar in Philadelphia when he confronted another man who he thought had thrown a rock at him and his friend.
In footage of the alleged incident posted on gossip website TMZ, the man is seen on the ground clinging to Hemsworth's leg, before the actor punches him in the face and pushes his head down, while his pal helps hold the guy down.
Police arrived at the scene and dispersed the crowd, but no official reports have been filed.
Hemsworth and his friend left and the unnamed man - who was bleeding - said: "I don't think [Liam] fared much better."
However, sources on the scene said that the 22-year-old actor - who was in the city working on new movie Paranoia - was unhurt and that, despite his claims, no one saw a rock get thrown.
Calls made to Hemsworth's representatives by TMZ have not been returned.
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