A driver was killed today and two paramedics seriously injured when the stationary ambulance where they were treating a motorist was crushed under a lorry, UK emergency services said.
Avon Fire Brigade said the accident happened on the eastbound carriageway of the M4 between junctions 18 and 17, near Tomarton, at 4pm.
The lorry, which was carrying prefabricated steel work, hit the Avon ambulance from behind as the two paramedics were treating the male driver of a car, the Fire Brigade spokesman said.
An Avon and Somerset Police spokesman said the man, who was being treated for chest pains, was killed instantly in the crash.
One paramedic suffered severe head injuries and was airlifted to hospital and another has multiple injuries and was taken to hospital by ambulance.
Both were in Frenchay Hospital, Bristol, with another civilian who was injured.
The driver of the lorry was suffering from shock.
"The ambulance has been totally destroyed and the large goods vehicle has landed on its roof," the Fire Brigade Spokesman said.
"Its load of steel is all across the motorway and it is currently leaking diesel fuel on to the motorway."
Environmental health officers had been informed and police accident investigators are dealing with the incident, the spokesman said.
The third lane of the eastbound carriageway of the M4 between junctions 17 and 18 was reopened at 6.40pm after the road was closed, police said.