Police are hunting a group of boys who attacked a train by dropping a concrete slab from a bridge.

The 39-year-old driver had a miraculous escape after being struck in his cab.

He was treated in hospital for neck and head injuries after the attack as the train travelled at 75mph along the East Coast Main Line.

Police said the incident on Thursday last week could easily have ended in a murder inquiry as the 10lb slab came within inches of hitting the driver directly on the head.

Det Sgt Brian Buddo, of British Transport Police, said: "The driver is a very, very fortunate individual.

"If it had hit him in the head it would have killed him and we would have been looking at a murder investigation.

"In my opinion, this was a deliberate act of vandalism."

Three youths, possibly aged as young as 11, are being hunted by police.

The incident happened just after 8.45pm on the road bridge leading to Littleburn Industrial Estate, just off the A690, at Durham City.

The Northern Trains pacer train was travelling northbound from Darlington to Newcastle. Police said the driver was the only person on board.

As he passed under the bridge, he saw a youth dressed in black clothing drop the slab over the edge of the bridge parapet. It crashed into the cab 20ft below, showering the driver with glass.

He suffered neck injuries, cuts and bruises and was taken to hospital in Newcastle, although he was later released after treatment. His employers said he was too badly shaken by the incident to speak to the media.

Police suspect the missile may have bounced either off the roof of the cab or the back of the driver's seat before hitting his head or his injuries could have been considerably worse.

The train was taken to a depot in Newcastle, where it was being examined by Northern staff.

Witnesses said there were three children, aged about 11 to 13, on bikes in the area before the attack. They may have stood on their bikes to look over the bridge parapet and aim the missile.

A spokesman for Northern said they were working with British Transport Police to catch the youths. "Unfortunately, incidents of this nature are not rare and we are committed to finding and prosecuting people who cause mindless vandalism."

Coun Maureen Smith, who represents Langley Moor and Meadowfield on Durham City Council, said she was shocked at the attack, particularly because the area had no history of such vandalism.