Tesco is "finalising" job cut plans but has declined to comment further.
Earlier, the Mail on Sunday reported that the supermarket could cut 15,000 jobs and close some fresh food counters and bakeries.
In an internal company email seen by the BBC, its chief operating office said plans were "still being finalised".
He also acknowledged that "any changes" would be hard for the people affected and said more information would follow.
More than 10,000 jobs have been cut at Tesco since the current chief executive, Dave Lewis, took over in 2014.
The UK's biggest grocer is in the midst of trying to save £1.5bn as the competition between supermarkets intensifies.
According to the Mail on Sunday, the grocer triggered a review of jobs after a particularly tough Christmas trading period.
The paper said the planned cuts would affect the majority of Tesco's 732 larger stores and put some of its meat, fish and delicatessen counters at risk.
It also said Tesco was also considering an overhaul of in-store bakeries - using frozen instead of fresh dough - and replacing staff canteens in some stores with vending machines.
Details of the cuts are likely to be announced this week, it said.
'Unsettling for everyone'
Tesco declined to comment on the claims but said it was "always looking at ways to run our business more simply and efficiently".
However, in a memo to staff, chief operating officer Tony Hogett acknowledged the media speculation.
"We are committed to tell our colleagues first of any changes we make as we continue to refresh and simplify the way we serve customers in our stores," he told employees.
"These changes are still being finalised, but as a result of this leak and speculation, we will bring forward our communications to give more information as soon as possible.
"We recognise that any changes will be hard for impacted colleagues, and unsettling for everyone. Our priority is to support our colleagues throughout."
The main union representing Tesco staff, Usdaw, called the media speculation "distressing" for staff.
National Officer Pauline Foulkes said: "It is appalling that they should hear about the future of their jobs in this way. Usdaw is seeking an urgent meeting with the company to clarify the situation, to examine the details of what changes they are proposing and what this means for staff.
"Our priority will be to press Tesco to confirm the details of their proposed changes to stop any further speculation."
Unite, which represents 800 workers at four Tesco distribution centres, called the reports concerning and said it too would be seeking clarification from Tesco.
