The chief constable of Greater Manchester Police, Peter Fahy, condemned lax security arrangements at shops after fights broke out and huge crowds threatened to cause crushes.
At least three people were arrested and a woman was hurt after being hit by a falling television, while some outlets were forced to shut to restore order.
Witnesses described how bargain-hunters behaved “like animals” and likened scenes to “a war zone”.
Fahy — whose force appealed to shoppers to “keep calm” — said: “The events were totally predictable and I am disappointed that stores did not have sufficient security staff on duty.
“This created situations where we had to deal with crushing, disorder, and disputes between customers. It does not help that this was in the early hours when police resources are already stretched.”
A number of outlets around the country opened at midnight as chains offered big price cuts to mark Black Friday, a phenomenon originating in the US which has emerged as one of Ireland and Britain’s busiest shopping days of the year.
GMP said officers were called to seven Tesco stores across the area. A post on the force’s Twitter feed said: “Keep calm, people!”
At least two people arrested at #BlackFriday sales events already this morning. Keep calm people!— Greater Manchester Police (@gmpolice) November 28, 2014
Shortly after midnight a 42-year-old man was arrested on suspicion of assault at a Tesco on Burnage Lane, Green End. Another man was arrested on suspicion of a public order offence after police were called to reports of fighting between some in a 300-strong crowd at a Tesco in Hattersley.
A third man was arrested shortly after 1am at a Tesco in Salford, after he threatened to “smash” a shop worker’s face in, police said.
Officers were called to four other Tesco branches across the area to deal with large crowds, including in Stretford, where fights broke out and a woman suffered minor injuries after being hit by a falling television.
Police were called to three Tesco branches in London following reports of large crowds. Images posted online showed chaotic scenes in Edmonton, with witnesses describing “mayhem” as discounted coffee machines went on sale.
Metropolitan Police Sergeant Paul Marshall said on Twitter: “Even on Black Friday shoving people to the floor so you can get £20 off a coffee maker is still an assault.”
South Wales Police also reported receiving a number of calls from staff at Tesco stores after they became “concerned due to the volume of people who had turned up to sale events”.
There were also disturbances in Scotland.