Marks & Spencer and Co-op stores are dealing with supply challenges and sparsely populated shelves as the fallout from the devastating cyber attacks continues.
The Co-op has confirmed it is now dealing with some shortages in its stores, while M&S has paused its online orders and is also experiencing empty shelves.
In an update to Co-op member-owners, the chain's CEO Shirine Khoury-Haq said: "The criminals that are perpetrating these attacks are highly sophisticated and our colleagues are working tirelessly to do three things: (1) protect and defend our Co-op, (2) fully understand the extent of the impact caused by the attack and (3) provide much needed information to the authorities that may help them with their investigations.
"Actively managing the severity of the attack has meant shutting down some of our systems to protect the organisation.
"That said, our front-line colleagues are focused on minimising any disruption that might be experienced by our members and customers."
The Times is reporting the Scattered Spider hacking group behind the attacks managed to trick IT helpdesk staff into resetting passwords.
The group reportedly carried out a "social engineering" attack on the Co-op, and a similar technique was adopted with the M&S hack.
In response, the National Cyber Security Centre (NCSC), part of GCHQ, has now issued new guidance to combat the techniques used by the hackers, including impersonating staff and tricking IT helpdesk employees.
FTSE 100
The UK's flagship share index, the FTSE 100, was up 65 points at 8,622 shortly after opening this morning.
Brent crude oil futures were up 1.69% at $61.32 a barrel.
Companies reporting today:
Advanced Micro Devices* - Q1 Results
International Workplace - Q1 Trading Statement