Don't react if you see someone dressed up as a clown - because that's exactly what they're after. Police say people dressing up as clowns could be 'anti-social behaviour fuelled by reports on social media'.

Pranksters in Norfolk are copying the clown who became an internet sensation. Photos of a clown who appeared at night on the streets of Northampton went viral after they were posted online.

Creepy Northampton clown set to scare park visitors at Pleasurewood Hills in Lowestoft

Footage appeared around the world of the clown, who waved at passers-by, before he was unmasked last month as a 22-year-old student.

Since then, copycat clowns have appeared in towns around the country. Now police say there have been two sightings of people dressed as clowns in King's Lynn this week.

The first was on Tuesday, November 26, at approximately 8pm on Marsh Lane, Gaywood. The second took place the following evening on the cycle path between the Fairstead skate park and Extons Road, at approximately 7.20pm.

Supt Carl Edwards, of Norfolk police, said: 'Firstly I'd like to stress that it isn't against the law to dress up as a clown.

'Nobody has been assaulted and it appears that the people involved are waiting for a passer-by to be startled by their appearance and run away, and then the clown runs after them for a short distance.

'We know there has been a lot of gossip and conversations about this on social media channels, not just in Norfolk, and it is important to gain a perspective on these incidents.

'We appreciate this can worry people, especially the young or elderly. The most effective way to behave if you are to see someone dressed up is to give no reaction – because that's what they are after.

'We will be out in the areas where reports have been made to attempt to find those responsible and offer them strong words of advice.'

In Tuesday's report, the person was described as wearing a full clown outfit with red suit and red hair. Those involved in the following day's sighting were wearing clown masks.

In both cases, the callers reported being alarmed and being chased a short way up the road by those involved.

Ian Ashford, owner of fancy dress shop Castle Costumes, in King's Lynn's Norfolk Street, said he had heard rumours there was a person going around dressed in a clown costume.

But he added: 'No-one's come in and bought a clown costume from us, I haven't had anyone come in and buy a clown since hallowe'en.'