The front of the train and a front window frame were damaged during the incident which happened when the Northern Rail Leeds to Sheffield service passed through the Newlands area at about 6.30pm.

Nobody was injured in the attack.

British Transport Police are hunting two suspects spotted on the bridge by the train driver.

Insp Glen Alderson said: "It's vital that we catch those involved. I can't emphasise strongly enough the dangers associated with this type of crime.

"This type of behaviour can have serious consequences. Throwing objects at trains is a serious offence and we will arrest anyone found committing such an act.

"There is also potential for a serious accident or injury - the driver was lucky not to sustain a serious injury.

Anyone with any information should contact BTP in confidence on Freefone 0800 405040, quoting incident number 487/May 12 2008, or Crimestoppers anonymously on 0800 555111.