YouTube footage has emerged of what appears to be fans of the Russian national side punching and kicking stewards inside Wroclaw's Municipal Stadium.
One helpless steward is knocked to the ground and then set upon by a group of supporters, while another is the recipient of two horrific kung-fu style kicks to the face.
The footage comes after police were forced to separate Russian supporters fighting Ukraine fans on the streets of Lviv in the early hours of Saturday.
The two sides exchanged a few punches at the Fan Zone before local police quickly moved in and separated the combatants. No arrests were made.
Tensions between the two nationalities are particularly high in Lviv, in the far west of the country, in part because of Ukrainian resentment at Soviet rule from 1939 to 1991.
The Lviv region was the centre of a resistance campaign by Ukrainian nationalists fighting for independence from the Soviet Union during and after World War Two.
Russia, who are managed by Dick Advocaat and set to host the 2018 World Cup, ran out comfortable 4-1 winners in the Group A clash, but the brilliant victory is likely to be tarnished by the actions of a minority of supporters.