Austrian police detained 157 mainly German fans yesterday in Klagenfurt, where Germany beat Poland, with most of the arrests made when supporters began chanting Nazi slogans in the city centre.
Polish and German fans, who had travelled in large numbers for the emotionally-charged match, also clashed in the city's public viewing areas and needed to be separated by police.
"Yesterday was the day of reckoning for us after four years of preparation," said a spokesman for Klagenfurt police today.
"There were challenges everywhere, but due to the information provided by hooligan spotters police could take precise and timely action," he said.
Some 80,000 fans travelled to Klagenfurt, the tournament's smallest city with a population of just 91,000. Around 30,000 came from Poland, 25,000 from Germany and 5,000 from Croatia.
Of the 157 detained, 144 came from Germany, 10 from Poland, two from Austria and one from Slovenia.
Wolfgang Rauchegger, police commander for the local province of Carinthia, said Austrian and German police detained a group of 140 potentially violent German fans who had congregated by prior arrangement in the city.
"They shouted Nazi slogans," he said.
Witnesses reported hearing the group shout "Sieg Heil", among other Nazi chants.
Four of them had police records as violent individuals.
Germany play Croatia in another game in Klagenfurt on Thursday, and tens of thousands of Croats are expected to descend on the city.
Mr Rauchegger said 30 Croatian hooligan spotters would mingle with fans and they expected some violent fans to try to travel to Klagenfurt. Asked how known troublemakers had managed to reach Austria from Germany, despite the re-introduction of border checks, Mr Rauchegger said they had probably slipped through spot checks at the frontier.
An Austrian national police spokesman declined to say how many fans travelling from Germany had been denied entry to Austria, but said the number was in double figures.
Some 3,000 police had been on duty for the game in Klagenfurt yesterday, including 400 German officers.
The arrests recalled scenes in the German city of Dortmund during the World Cup, where police detained more than 400 people after outbreaks of violence in the run-up to the Germany-Poland match.