Some 20 people were reported injured when two cranes collapsed onto housing in a western Dutch town on Monday as they attempted to hoist a large section of a bridge into place across a waterway, the Dutch public broadcaster said.

Footage posted on Twitter showed the cranes teetering and then collapsing onto houses on one side of the waterway. The houses, barely half the height of the cranes, appeared to have been crushed by the falling cranes and the bridge section.

Emergency services in Alphen aan den Rijn confirmed the accident on Twitter. "There are reports of several wounded," the service tweeted. Dutch public broadcaster NOS reported that 20 people were injured, many of them seriously.