Interior Minister Wolfgang Schaeuble said Berlin would temporarily suspend the European Union's Schengen travel agreement to allow it to make border checks.

Travellers in the Schengen zone of 15 European countries can normally move freely across borders without showing an identity card, but member states can suspend the accord and reintroduce controls at times of heightened security alert.

Terrorism and hooliganism are the chief concerns of German officials as they prepare to host the month-long World Cup, one of the biggest events in sport.

More than a million foreign fans will attend the 64 matches and an unknown number will travel to Germany even though they have no tickets for the games.