A man has died after a stage collapsed before a Radiohead concert in Canada, with onlookers claiming "it was like a tornado had hit".

Three other people were injured, one seriously, at the Downsview Park in Toronto, on Saturday.

The incident happened an hour before gates were due to open for the 40,000 sell-out show. The man who died was in his 30s and had been involved in setting up the stage. He became trapped under the rubble and was pronounced dead at the scene.

Onlooker Jaime Rivest said the stage and scaffolding suddenly began falling down.

"It was like a tornado hit the stage and in just moments the stage came down with metal everywhere," he explained.

Emergency Medical Services deputy commander David Viljakainen said the top section of the stage had collapsed while it was being set up.

Radiohead soon announced the show had been called off.

"Due to unforeseen circumstances tonight's at Downsview Park, tonight has been cancelled. Fans are advised not to make their way to the venue," said a statement on their Twitter account early on Saturday evening.

The show was due to be their last North American concert before the British group fronted by Thom Yorke - travel to Europe.

It is not yet known what caused the stage to collapse.