The assistant chief constable of Norfolk police has criticised people who used Twitter and Facebook to post 'fictitious and malicious rumours' that civil unrest had spread to the county's streets.

Assistant chief constable Charlie Hall also urged shopkeepers to adopt a 'business as usual' approach after some shops shut early yesterday.

Norfolk police stepped up patrols around the county yesterday and has pledged the high visibility approach will continue today.

While violence spread to places such as Manchester, Gloucester, Nottingham and Birmingham last night, there were no incidents in Norfolk.

Mr Hall said: 'We are extremely pleased with the way the public has reacted to our earlier messages. Overnight there was a strong sense of calm and we intend this to remain the same.

'Police would like to dispel fictitious and malicious rumours which are circulating, particularly on social networking sites about disorder on the streets of Norfolk.

'We understand how distressing these rumours must be to residents of Norfolk and can assure people there is no substance in them. Our stance remains the same as yesterday - we have sufficient police officers to maintain a high-profile presence whilst at the same time assisting the Metropolitan Police.

'We would urge retailers to adopt a business as usual approach to opening hours following reports some shops closed early yesterday.'

Specialist police officers from Norfolk are still providing support to the Metropolitan Police in response to the civil unrest in London and other parts of the country.

But Mr Hall said the force has kept in place extra resources to ensure that they can deal with any local issues and to reassure communities.

Mr Hall said: 'Our Safer Neighbourhood Teams will be providing reassurance patrols conveying the message to residents and businesses that there is no intelligence to suggest that a repeat of what has occurred in London and elsewhere is likely to happen locally.

'Where possible, PCSOs and police officers and Special Constables will be spending additional time in their neighbourhoods, talking to local people.

'By working together, Norfolk has sufficient police officers and PCSOs to look after their communities as well as assisting other forces.'

Last night, messages posted on social networking sites Twitter claimed riots had arrived in Norwich and that looters had struck at Anglia Square and PC World, which was not the case.

Shops in Norwich's Royal Arcade closed early yesterday following concerns that civil unrest in London could spread to other cities.

John Fielding, managing director of Langleys Toymaster, in the Royal Arcade, said then: 'We were told to close early because the landlords have told the caretaker to the arcade to close the gates early.

'The landlords are based in London and I suppose if I was based in London I would be a bit more worried about the situation.

'However, this isn't London and I think they're being over cautious and over zealous.'