Two people died and at least 18 were injured in a strong explosion that rocked a four-storey building being renovated in central Madrid on Friday, Spanish authorities said.

Two men working on the building died in the explosion, Madrid's Mayor Jose Luis Martinez-Almeida said on Friday evening. Of the 18 people hurt, most of the injuries were not serious, officials said.

Earlier, he said four people had been taken to hospital, one in serious condition. The cause of the blast was not yet clear.

(Cover image: A woman walks past debris and damaged vehicles, following a suspected gas explosion in Madrid, Spain May 6, 2022 /Reuters)