London (CNN) -- Violence linked to last week's shooting death of a 29-year-old man broke out for a third consecutive day Monday -- this time in daylight -- with gangs of youths attacking a police car and shops in the Hackney area of East London.
Video from the scene showed riot police involved in skirmishes around Hackney, youths destroying a police car, smashing shop windows, a sporting goods shop being looted and the window of another shop being smashed.
Riot police cordoned off one of the main streets and blocked traffic.
Metropolitan police said: "There is disorder in the Hackney area, the police are on the scene and are dealing with it. No injuries have been reported to us at this time."
The renewed unrest came after police announced the arrest of more than 100 people Sunday night and early Monday in
connection with riots Saturday night in the city's Tottenham neighborhood and continued violence in isolated outbreaks elsewhere in the city on Sunday.
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Saturday night's violence started in Tottenham, an ethnically diverse, working-class suburb north of London's center whose residents are predominantly Afro-Caribbean. Saturday's riots had been sparked by the shooting death Thursday of Mark Duggan as he was seated inside a cab.
Officers from Operation Trident -- the Metropolitan Police unit that deals with gun crime in London's black communities -- stopped the cab during an attempted arrest and soon afterward shots were fired, the Independent Police Complaints Commission (IPCC) said. Duggan, a father of four, was fatally shot. Shooting deaths are rare in England.
The commission divulged neither who shot the 29-year-old black man, nor why police had stopped the cab.
Some reports suggested that Duggan was held down by police and shot in the head, but the IPCC has denied this.
"Speculation that Mark Duggan was 'assassinated' in an execution style involving a number of shots to the head are categorically untrue," the IPCC said in a statement.
A British police watchdog group said evidence from Thursday's shooting scene, including a nonpolice firearm, was to undergo forensic testing.
Rachel Cerfontyne of the police complaints commission said that, while the shooting remained under investigation, "speculation that Mark Duggan was 'assassinated' in an execution-style involving a number of shots to the head are categorically untrue."
Hanstock, the police commander, called Duggan's death "extremely regrettable."
"It is absolutely tragic that someone has died, but that does not give a criminal minority the right to destroy businesses" and "steal from their local community," he said.
The man's family and friends, who have blamed police for the death, gathered outside the Tottenham police station Saturday night to protest.
What began as a peaceful protest soon devolved into riots as demonstrators -- whose numbers included whites and blacks -- tossed petrol bombs, looted stores and burned police cars.
They pelted officers with bottles and bricks as riot police charged at the crowd and blocked streets. A double-decker bus and buildings were set ablaze.
"There was no indication that the protest would deteriorate into the levels of criminal and violent disorder that we saw," Police Cmdr. Adrian Hanstock said. "We believe that certain elements, who were not involved with the vigil, took the opportunity to commit disorder and physically attack police officers, verbally abuse fire brigade personnel and destroy vehicles and buildings."
The arrests were in addition to 61 others made Saturday night and Sunday morning. Sixteen people were charged, and at least 17 people have been released on bail, police said.
The unrest prompted Home Secretary Theresa May to cut short her summer vacation and return Monday afternoon to London.
"Last night, police officers again put themselves in harm's way to protect Londoners and their property," May said Monday. "Those responsible for the violence and looting will be made to face the consequences of their actions. Many have been arrested and further arrests will be made."
In all, 35 police officers have been injured since the violence broke out, Metropolitan Police said.
Also Monday, firefighters battled a blaze in a shoe store.
"Groups of youths are continuing to target shops," but more police officers have hit the streets since Saturday's riots.
"This is a challenging situation with small pockets of violence, looting and disorder breaking out on a number of boroughs," said Commander Christine Jones of the Metropolitan Police, also known as Scotland Yard.
Police said the rioting and looting in other parts of the capital were "copycat" events conducted by opportunists and criminals.
On Monday morning, residents of the commercial center of Brixton south of London awoke to see the aftermath of Sunday night's sporadic shooting in the commercial center. A KFC's windows were smashed, a Foot Locker store was burned, and the main street was closed as police investigators combed through the area looking for evidence.
Police said they were reviewing closed-circult television footage in an attempt to identify looters.
Looting also occurred in pockets of Enfield, next to Tottenham, in London's north end.
Daniel Levy, chairman of the Tottenham Hotspur Football Club, said Monday that members of the club -- a major business in the area -- were "deeply saddened" by the events.
"We are concerned about the disruption to local people's lives and the effect on the community as a whole," Levy said in a statement. "The situation has also meant that vandals have unfortunately been able to use the events as an opportunity to loot and destroy property and business premises."
On Sunday, British Prime Minister David Cameron's office called the rioting "utterly unacceptable."
"There is no justification for the aggression the police and the public faced, or for the damage to property," it said in a statement.
"The scenes of violence and destruction over the weekend are utterly appalling," said London's Mayor Boris Johnson, in a statement. "People have lost their homes, businesses and livelihoods through mindless violence. I understand the need for urgent answers into the shooting incident that resulted in the death of a young local man, and I've sought reassurances that the IPCC are doing exactly that. But let's be clear these acts of sheer criminality across London are nothing to do with this incident and must stop now."
A representative of Johnson said Monday evening that he was cutting short his family holiday in North America to return to London.
"This is not about the black community and the police, it's about young people and the police," said Shaun Bailey, a youth worker, in a statement circulated by the mayor's office. "And let's not beat around the bush and pretend this is some type of social justice protest -- it's sheer criminality."
On Sunday, when police patrols were increased, there were scattered reports of looted shops and smashed-in storefronts, but the earlier widespread violence was not repeated.
The possibility of such violence was a concern to David Lammy before it occurred. The Labour MP for Tottenham told a reporter in March that Tottenham could become a scene of violence as cuts to social-service programs for youths were implemented. "It's heartbreaking," he told the Tottenham & Wood Green Journal. "I'm really worried that the social experiment that we're seeing from the Tory-led coalition will lead to scenes akin to something that we see in some of the inner-city areas of America and that's why we need to bring this government down."
But the leader of Enfield Council, Doug Taylor, was unmoved. "There can be no justification for the violence and the looting," the Labour Party member told a reporter.
Deputy Prime Minister Nicholas Clegg called the rioters "opportunists -- cynical folks who are indulging in smash-and-grab criminality."
CNN's David Wilkinson, Atika Shubert, Byrony Jones, Erin McLaughlin, Bharati Naik, Aliza Kassim and David Wilkinson contributed to this report.
