Bosnian authorities have ordered police in areas where Croats and Muslims live side-by-side to beef up up ahead of the Euro 2008 quarter-final between Croatia against Turkey, reports said on Thursday.
It was presumed that while Croats would support their compatriots, Muslims may root for Turkey at Friday's match which takes place in Vienna, reported dpa.
Bosnia was embroiled in a brutal ethnic conflict 1992-1995. Though Muslims and Croats on one side mostly fought Serbs on the other, Croats and Muslims also fought each others in some areas.
Concerned that football may provide a spark for violence amid old tensions, an extra 700 police, including commandos, were raised to secure order in hotspots such as the divided town Mostar in southern Bosnia.
During the 2006 World Cup, a massive street brawl followed Croatia's match against Brasil in Mostar, when Muslims from the eastern section marched to taunt Croats in the west. Six policemen were injured, 30 people arrested and many cars and buildings were damaged.
Tighter security was also ordered in prisons, where trouble also routinely follows sport events.