The gang members seemingly take delight in injecting humour into their raids, which rely on sheer numbers and the confusion caused by their presence. After they plundered Kobe beef fillets, champagne and smoked salmon from a gourmet store on the exclusive Elbastrasse, they presented the cashier with a bouquet of flowers before making their getaway.

The latest robbery is part of a pattern over the past several months, suggesting that the thieves deliberately set out to highlight what they perceive as the inequality inherent in German society.

However, the authorities do not agree. Bodo Franz, a police spokesman, said: "They get off feeling they are just like Robin Hood. There are about 30 in the group. But whatever their motives, they are thieves, plain and simple."

Carsten Sievers, the manager of a luxury supermarket in the wealthy Blankenese area of Hamburg, recently watched the robbers run off with trolleys full of expensive foodstuffs, including Kobe beef which, at more than £100 a pound, is always on their illicit shopping list.

In another recent swoop, the gang emptied a groaning buffet table in a top restaurant into sacks, while one of their number held up a sign saying. "The fat years are over" - the title of a hit film currently doing the rounds in Germany.

In internet statements, the gang have made a point of saying their booty is distributed to Hartz IV recipients - the poorest of Germany's long-term unemployed. The benefit is named after the disgraced Volkswagen personnel director Peter Hartz who, before he lost his job with the car-maker in a prostitutes-and-bribes scandal, devised the new means-testing which is loathed and derided by society's most economically challenged.

When the gang robbed the gourmet store in April - triggering a massive police investigation that cost £20,000 in taxpayers' money without an arrest being made - they left a note behind saying: "Without the abilities of the superheroes to help them, it would be impossible for ordinary people to survive in the city of the millionaires."

Police say they are concentrating their investigation on a loose collective of anarchists and malcontents called "Hamburg in Vain", to which they believe the superheroes belong. But they admit there is a certain panache and skill about their robberies. indicating a strong criminal element as well.

The gang are also behind black market cinema tickets which they distribute free to the poor, and they have printed leaflets telling passengers how to dodge ticket inspectors on the city's underground and buses.

Mr Franz said: "They try to make crime fun but are politically motivated."