Italian authorities say two people have died, at least 60 people have been injured and a bridge has partially collapsed following a major explosion on a highway near the northern city of Bologna.

Police said in a statement that between 60 and 70 people were injured, some with serious burns.

The Italian news agency ANSA reported a tanker truck carrying flammable material exploded after running into the back of another truck.

The charred remains of a truck hang from a partially collapsed overpass of the highway. ( AP: Giorgio Benvenuti )

A police video showed the tanker failing to brake and ploughing into the rear of a truck stopped in traffic.

"The shockwave from the blast was extremely violent. Many of the injured received cuts from flying glass, which had shattered," said Giovanni Carella, the emergency coordinator for the local fire service.

Sorry, this video has expired It's thought one of the trucks in the crash was a tanker with flammable materials. (Photo: Twitter/@amemacula)

Italian firefighters said they sent multiple rescue and emergency squads, including one from their urban search and rescue team.

Part of a bridge collapsed and fire spread to a carpark below the bridge, where several other vehicles caught fire and exploded.

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A video shot from a parked car at the moment of the explosion appeared to show someone being engulfed by flames when the tanker exploded.

Authorities said the accident closed down a major interchange connecting highways linking northern Italy with the Adriatic coast, a popular destination as Italy heads into next week's peak summer holiday travel period.

Local media say at least one person was killed and dozens injured. ( Vigili Del Fuoco via AP )

AP/Reuters