Stockholm  - Swedish police on Sunday reported multiple arrests in connection with a spectacular cash heist in which thieves used a helicopter to raid a security firm in Stockholm.

A police spokeswoman declined however to give the exact number of people arrested or their backgrounds.

The criminals used a stolen helicopter and explosives in an early morning raid on Wednesday at the G4S cash depot in the suburb of Vastberga.

They escaped with an undisclosed amount of cash, having given themselves a headstart by planting a fake bomb near the police helicopter that would have been used in any pursuit.

The criminals' helicopter was later found abandoned in a field north of the Swedish capital.

G4S has offered a reward of 1 million dollars for information leading to arrests.

Aviation experts said the pilot who flew the helicopter was likely very skilled, citing the pre-dawn flight to the depot building and the location of landing site close to high trees.  dpa