Police on Wednesday said they have arrested 56 suspected Polish football hooligans in Dortmund, where Poland was meeting Germany in a much-anticipated World Cup match in the evening.

Police spokesman Wolfgang Wieland said some of the men were arrested because they were found with dangerous objects, while other were believed to be "potentially or certainly violent".

At least seven of the men were arrested after they were stopped and searched in downtown Dortmund and found to be carrying the kind of gumshields worn by boxers.

It gave the impression that they could be bracing for clashes with German fans in the western city, the spokesman said.

Rafal Wasaik, a Polish police captain deployed in Germany for the World Cup, told reporters: "We have arrested people who could cause trouble. They were recognised by my Polish colleagues."

He said the men had been taken to the police station for questioning and would be released "either before or after the match", depending on whether the police found they posed a real threat or not.

Police were expecting about 30 000 Polish fans to show up for the Group A match between the host nation and the Poles, whose hopes of reaching the second round were later crushed by defeat.

Eleven Polish police officers who are experts on dealing with hooligans have been deployed on the streets of Dortmund.

Wieland said a few hours before kick-off there were already some 10 000 Polish and Germans fans out on the street, but that the atmosphere was peaceful.

"There have been no clashes," he said.