At least two people have been arrested at "Black Friday" sales across Greater Manchester this morning.
The Greater Manchester Police (GMP) confirmed the news and called for calm.
The GMP was also called to seven Tesco stores across Greater Manchester following disturbances at "Black Friday" sales events.
A police spokesperson said fights broke out between shoppers at some stores and one man was arrested on suspicion of assault after his conduct in store was challenged by staff.
GMP alleged that he threatened to "smash" a staff member's face in.
Sir Peter Fahy, chief constable of GMP, said he was disappointed that the stores did not have "sufficient" security staff on duty.
"This created situations where we had to deal with crushing, disorder and disputes between customers," Fahy said.
"It does not help that this was in the early hours when police resources are already stretched.
"Across Greater Manchester large supermarkets already make significant demands on policing through calls to shoplifting, anti-social behaviour and thefts of fuel from their petrol stations - much of which is preventable.
"We just ask these stores to work with us to reduce the demands on policing and reduce the risks of disorder and crime."
Tesco had not responded to a request for comment at the time of publication.