Co-op is facing availability issues in some stores as it continues to combat “sustained malicious” cyber attacks.

The convenience retailer’s systems were first hit by an attack last week, when back-office systems and call centre services were hacked. It has since experienced product shortages, particularly across categories such as fruit and vegetables, meat, and dairy.

According to The Telegraph, a sign in one affected store read: “Sorry, we’re having some availability issues which will be resolved shortly.”

Meanwhile, images posted on social media show empty fridges and shelves. It is understood that some stores have received limited stock deliveries in recent days.

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In a statement, a Co-op spokesperson said: “All our stores are open and trading however, due to the sustained malicious attempts by hackers to access our systems, we have taken proactive steps to keep our systems safe, which is temporarily impacting our colleagues’ ability to perform their roles and how many deliveries we can make to our stores.

“This means that some of our stores might not have all of their usual products available and we would like to say sorry to our members and customers if this is the case in their local store. We are working around the clock to reduce disruption and resume deliveries.”

The convenience chain confirmed on Wednesday last week (30 April) that it had to shut down parts of its IT systems in response to hackers trying to gain access.

Co-op encouraged staff to keep their cameras on during virtual work meetings as the business deals with the cyber attack. It emailed employees asking them to be vigilant as IT teams work to protect the systems.

M&S has also been battling a cyber attack over the past two weeks, which has seen some of its IT systems go down, with shelves empty, online services suspended, and warehouse employees sent home.

The high street retailer’s ransomware attack has been linked to the Scattered Spider group, a cyber gang reportedly involving both UK and US-based hackers.