Warnings of a potential terrorist threat to soccer's World Cup hold chilling associations for the city of Munich as it prepares to host the opening match under the gaze of billions of TV viewers.

The German players who will take the field against Costa Rica on Friday are too young to remember the massacre of 11 Israeli athletes by Palestinian "Black September" guerrillas at the 1972 Olympic Games in Munich.

A woman rest in front of an illuminated fountain in Munich's centre near an university on May 27, 2006. The FIFA soccer World Cup 2006 will be held in Germany from June 9 - July 9.[Reuters]

But the experience of seeing the "Friendly Games" turn into a bloodbath left deep scars on Germany, provoked a radical security shake-up whose results are still visible, and remains very much in the minds of police and officials.

"I believe it's an abiding memory and a warning for Germany," says Gregor Rosenthal, a senior interior ministry official helping to lead the copious security planning for the 32-nation World Cup.

Officials say there is no concrete indication that Islamist militants are planning attacks during the tournament, although the general "abstract risk" is high.

They say the opening match in Munich and the July 9 final in Berlin would present the most symbolic, and therefore most attractive, targets.

The massive security net includes NATO air patrols, flight bans over stadiums, 250,000 police on duty around the country and a comprehensive intelligence-sharing network with a round-the-clock unit in Berlin at its nerve centre.

Special forces at the ready include the crack 240-strong GSG 9, created specifically in response to the Munich tragedy.

LESSONS LEARNED

In many ways, Munich 1972 was an object lesson in how not to handle a militant attack.

A series of blunders culminated in a bloody debacle at Fuerstenfeldbruck, an airbase where the Germans had provided the Palestinians with a getaway plane but planned to overpower them and free their Israeli hostages.

"We had never seen a terrorist, it was like something out of a bad TV cop film...We hadn't trained for that," recalls Heinz Hohensinn, 63, a Munich policeman who was part of the assault team but whose previous experience was limited to tackling robbers and drug dealers.

"The fully fuelled plane was standing there ready to take off, as the terrorists demanded," he told Reuters.

"We were supposed to overwhelm the terrorists in the aircraft before it took off, but that was a short-term emergency plan and it was abandoned as too risky because the leader had a hand grenade and we would all have been blown up with the plane. Then the shooting started..."

All the hostages were killed in the carnage, along with a German policeman and five of the kidnappers.

Security analyst Rolf Tophoven said Germany's desire to present a friendly face to the world at Munich -- in contrast to the Nazi-hosted Olympics in Berlin 36 years earlier -- was partly to blame for the lack of preparedness.

"The trauma of the Hitler Olympiad was in the minds of the German organisers...Security was low-profile in Munich because no one wanted to stir memories of German police and armed troops in 1936," he said.

Another generation on, and with the U.S.-led war on terrorism nearly five years old, German security is forewarned, better equipped and confident it can throw a great sporting party for the world.

"The training, weapons and technical equipment are all very different today...There's a lot more understanding of security and controls. The hospitality won't be dampened if the security is cranked up," Hohensinn said.

Officials believe they can show off their country as a fun-loving, welcoming host and keep the tournament safe without smothering it with security.

"We have our tournament motto -- "A Time to Make Friends" -- and that means above all that sportsmen and fans from all over the world will feel safe," Interior Minister Wolfgang Schaeuble said this week. "We need security for a joyful and happy World Cup."