Scotland Yard says it has arrested a total of 1,047 people in connection with the violence, disorder and looting in London, with 584 of them charged.
Police said they arrested a 22-year-old man over the murder of a pensioner who was attacked as he tried to stamp out a fire.
Richard Mannington Bowes, 68, died in hospital just before midnight on Thursday after he was attacked in Ealing, west London, on Monday.
The suspect was held in west London on suspicion of murder, rioting and carrying out three burglaries, Scotland Yard said.
Bowes suffered serious head injuries and was placed on a life-support machine following the attack, which happened at 10.45pm local time on Monday as violence spread through the capital.
In Greater Manchester, A 15-year-old boy was arrested for looting after his mother handed him in to police as the hunt goes on for more suspects.
The woman saw pictures of rioters trying to prise open the shutters of a shop in Salford as the shopping precinct was being looted on Tuesday evening.
She recognised her son as one of the looters and took him to the local police station.
He is now under arrest on suspicion of burglary.
The boy is one of more than 200 people arrested across Manchester, Salford and Liverpool during the rioting earlier this week.
Garry Shewan, assistant chief constable of Greater Manchester Police, said: "The parent saw the picture of her son and was absolutely appalled, horrified and angry.
"What she did is extremely admirable and I thank her for handing him in to local officers as it must have been a hard thing to do.
"I would urge members of the community who were left angered by the events of Tuesday night and believe they know of those involved
to contact police as soon as possible."
Police in Manchester have now made 176 arrests following the rioting in the city and in neighbouring Salford on Tuesday night.
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