(CNN)The Croatian football federation has blamed "sabotage" after the imprint of a Nazi swastika was left on the pitch used for its national team's Euro 2016 qualifier against Italy Friday night.
Euro 2016: Croatia apologizes over Nazi swastika on its home pitch
The match at the Polijud Stadium in Split was already being played behind closed doors as punishment to the hosts for previous incidents involving its fans, but the few present and viewers on television could clearly see the notorious symbol.
Ground staff made largely unsuccessful efforts at halftime to remove the swastika sign. It was unclear if it had been mowed into the grass or placed there by other means.
The game finished 1-1, to leave Croatia top of Group H by two points from Italy, but it could face further sanction by European governing body UEFA.
Tomislav Pacak, a spokesman for the home federation, issued a statement about the incident on its official website Saturday.
"We apologize to all viewers, our guests from Italy and the players from both teams, for the Nazi symbol on the Poljud Stadium grass," he said.
"We have immediately notified UEFA of the incident.
"This was an obvious act of sabotage and a criminal act. We condemn it and ask the police and judicial bodies to find the person(s) responsible for what is a shame not only for Croatian football, but the entire country.
"Once again, we express regret and condemn this act, and we apologize to all the viewers, guests and players from both teams."
Pacak claimed that a "chemical agent" had been used on the pitch, 24 to 48 hours before kickoff, timed to be visible during the qualifying match.
The stadium is the home of Croatian top-flight side Hajduk Split.