German security authorities believe 21 World Cup matches are at high risk of terrorist attack.

The tournament-opening match between Germany and Costa Rica in Munich on June 9, the final in Berlin on July 9 and any match involving the United States were considered the top targets.

Matches involving nations which contributed troops to the US-led invasion of Iraq - Australia, England, Poland and Spain - could also be targets of Islamic extremists.

The German government has stressed that it has no indication of a credible terrorist threat to the 64-match tournament which will take place in 12 cities.

But the BKA is concerned that with security set to be tight at stadiums, extremists may turn their attention to the so-called Public Viewing Areas where fans can follow matches on big screens.

Some politicians said they saw nothing new in the report.

"The internal picture painted by the BKA doesn't surprise me. It corresponds to our previous assessment," said Ingo Wolf, the interior minister in the regional state of North Rhine-Westphalia.

"The security authorities have been preparing for the World Cup for years and have taken into account that countries which have taken part in the Iraq war are at particular risk from Islamic terrorism."