Some 27 young people, most of them children, were injured in Finland on Thursday when a temporary footbridge by a construction site collapsed and they fell several metres onto a road, rescuers said.

"Approximately 27 youths, mostly minors, have been injured, to varying degrees," the Western Uusimaa rescue department in Espoo, near the capital Helsinki, said in a statement.

The accident happened around 9:20 am when wooden planks are believed to have given way and the youths fell to the ground.

Helsinki hospital service HUS said "the injured belonged to a group of schoolchildren" and "the majority of the injuries are limb fractures."

Twenty-four of the injured have been transported to various hospitals in the region.

"No one has life-threatening injuries," HUS said in a statement.

Pictures from the scene showed the footbridge largely intact, with a pile of wooden planks laying in a jumble under one end.

Rescue workers could be seen treating multiple people laying injured on the road.

"Shocking news from Espoo. Our strength to those injured in the accident and their loved ones. You are in our thoughts," Prime Minister Sanna Marin said on Twitter.