Dundalk and Drogheda United fans fought on the pitch at Oriel Park at the end of their League of Ireland match on Friday.
Shortly after the final whistle of the match, which Dundalk won 4-2, a group of Drogheda United fans sprinted across the pitch towards their Dundalk counterparts and a fight ensued.
The fans were separated only after police intervened.
Three people were arrested.
It would have been hard for Drogheda fans not to go across with that song being played. Really rubs in the fact that Dundalk are the more successful club.