The hunt is on for a serial arsonist who targets post boxes in Sprowston and Thorpe St Andrew, on the outskirts of Norwich.

Police are stepping up patrols in the area after nine Royal Mail post boxes were targeted since mid-August.

Police continue to investigate the incidents and are urging members of the public who witness anyone acting suspiciously near a post box to call them immediately.

The first fires happened in Thorpe St Andrew between August 18 and 21 when post boxes in Harvey Lane, Orchard Close and Henby Way, were deliberately set alight.

Between August 25 and 28 the post box in Thunder Lane was targeted while between 6.30pm and 6.45pm a post box in Harvey Lane was set alight for a second time.

Four post boxes were targeted in Sprowston overnight on Saturday, September 8 in Blithewood Gardens, Cozens Hardy Road, Neville Road and Wroxham Road.

In all cases mail was damaged or destroyed as a result of the fires.

Local policing commander, Inspector Dave Cuff, said: 'Patrols have already been stepped up in the areas affected and this activity will continue.

'The majority of incidents have happened in the early hours and we believe they are being committed by the same offender.

'I would urge anyone in the area who witnesses people acting suspiciously, particularly near post boxes, to contact police immediately.'

A fire was also started deliberately in the public toilets at River Green, off Yarmouth Road in Thorpe St Andrew in the early hours on August 21.

Meanwhile, an arsonist torched a bin in St William's Way in Thorpe St Andrew just after 1.50am on Friday, September 14.

Anyone who witnesses suspicious activity is urged to call police using the non-emergency number 101 - if you believe a crime is in progress always dial 999.