Police have warned drivers to be careful after objects were thrown into the carriageway of busy roads in west Norfolk.

The warning from King's Lynn police comes after an incident on the A47, between the Pullover and Hardwick roundabouts, on Monday morning.

At about 8am, a white Ford Transit was travelling eastbound when an unknown object hit the windscreen, causing severe damage.

Amy Laws, investigating officer, said: 'It is currently unknown what has caused this damage. However, at this time, it is believed that an object may have been thrown from a flyover.

'The victim was travelling at approximately 60-70mph and if he had not acted so swiftly, or the roads were busier, the outcome could have been a lot worse.'

She said three other incidents involving HGVs travelling on the A47 near to Hay Green Road North had been recorded.

These incidents took place on Tuesday, July 5, Tuesday, July 19 and Tuesday, September 6 at about 4am.

On each occasion a golf ball-sized rock was thrown into the carriageway, smashing the windscreens.

PC Laws added: 'We treat reports of this nature very seriously because of the potential repercussions. I would like to warn motorists about this worrying trend and ask them to contact us immediately on 999 if they see someone acting suspiciously near to a flyover or the side of the road. '

• Anyone who witnessed any of the incidents or anyone with information about them should contact PC Amy Laws on 101.