The supermarket chain Spar has been forced to close scores of stores following a cyber attack. 

The outage, which first struck on Sunday, has left more than 300 shops unable to receive credit card payments or use email.  

Many branches were forced to shut, although some sites have managed to stay open by accepting cash.

It was unclear if any customer data had been compromised. 

The majority of Spar’s stores are run as franchises by different companies and they span five major areas in the UK. 

A spokesman said only stores in the north of England, run by distribution partner James Hall & Company, were affected. 

“We are working to resolve this situation as quickly as possible – [the issue is] not affecting Spar UK as a whole,” he said.

Customers complained on social media about the closures. 

One tweeted: “Anyone know what happened to Spar shops today? I’m currently visiting a friend in Whitby and went there for milk. Two Spar stores with fuel stations closed. Saw an attendant who said the whole till system has been down all day.” 

Spar was founded in the Netherlands in 1932 and it is one of the world’s largest food retailers with more than 13,000 stores in 48 countries. 

It has more than 2,500 stores in the UK that employ about 40,000 people and has an annual turnover of more than £3bn. James Hall & Company supplies products to almost 600 Spar stores. 

In October, Tesco’s website was knocked offline after an attempted hack that left customers unable to place orders. 

A spokesman at the Information Commissioner’s Office said: “We are aware of reports regarding an incident affecting Spar stores and we will be making enquiries.”

Companies are required to notify ICO within 72 hours if they believe customer data is at risk. 

 A National Cyber Security Centre spokesperson said: “We are aware of an issue affecting Spar stores and are working with partners to fully understand the incident.”