The prime minister cut short his holiday and flew back to Britain as London witnessed devastating scenes of violence stretching the emergency services beyond limit on a third night of rioting in the capital.

Buildings were torched, shops ransacked, and officers attacked with makeshift missiles and petrol bombs as gangs of hooded and masked youths laid waste to streets right across the city.

The sheer number of incidents – including in Hackney, Croydon, Peckham, Lewisham, Clapham and Ealing – seemingly overwhelmed the Metropolitan police at times, who had poured 1,700 extra officers onto the streets.

Disturbances continued into the early hours on a breathtaking scale, and they spread outside London for the first time with riots reported in Birmingham and Liverpool.

David Cameron, forced to break off from holiday in Tuscany, was this morning due to chair a meeting of the government's emergency committee, Cobra. He was travelling on a UK military flight leaving Italy at 3am. Asked why the prime minister had now decided to return, a Downing Street source said: "The situation has become more serious."

Officers from Thames Valley, Essex, Kent, Surrey and City of London were drafted in to support the Met. But apparent "copycat" riots continued to spread in the wake of Tottenham's riots on Saturday precipitated by the fatal shooting by police of Mark Duggan, 29, a father of four, last Thursday. So far 225 people have been arrested and 36 charged.

The violence erupted in daylight in Hackney, east London, where police confronted rioters hurling missiles and setting fire to bins and cars. One officer could be seen lying on the ground after being struck on his shield by a missile.

In Hackney's Pembury Estate, the centre of the violence in east London, masked youths – both men and women – helped carry debris, bins, sticks and motorbikes, laying them across the roads to form a flaming boundary to the estate.

Several buildings were set alight in Croydon, south London, one massive fire consuming the 100-year-old Reeves furniture store. The fires were so severe that approach roads into Croydon were thick with smoke leaving some residents struggling to see or breathe. "Words fail me. It's just gone, it's five generations. My father is distraught at the moment. It's just mindless thuggery," said owner Trevor Reeves.

A bus was torched in Peckham as police struggled to respond to the spread of sporadic incidents. Witnesses said a 100-strong mob cheered as a shop in the centre of Peckham was torched and one masked thug shouted: "The West End's going down next."

A baker's next door was also alight. One onlooker said: "The mob were just standing there cheering and laughing. Others were just watching on from their homes open-mouthed in horror."

A trail of bins and abandoned vehicles were ablaze in Lewisham.

At Clapham junction, looters – some as young as 14 – moved from shop to shop laughing as they smashed shop windows and clearing shelves of stock, unimpeded by over-burdened police.

Tim Godwin, acting Metropolitan police commissioner, made a direct appeal to parents to get their children off the streets. "I do urge now that parents start contacting their children, and ask themselves where their children are," he said. "There are far too many spectators who are getting in the way of the police operation to tackle criminal thuggery and burglary." He said "significant disorder" had broken out in many communities. These included incidents in Camden, Bethnal Green where a Tesco was looted and two officers hurt, Stratford, Notting Hill, Colliers Wood and Dalston.

Reassuring Londoners police were there in numbers, Godwin added: "We remain steadfast and determined."

The unrest spread beyond London with West Midlands police confirming outbreaks of disorder in Birmingham city centre. Shops including a branch of Louis Vuitton had windows smashed and were looted. An unmanned police station in Handsworth was torched. Extra officers were being sent into the streets of Britain's second city.

Merseyside police also confirmed 'a number of isolated outbreaks of disorder," including burning cars and criminal damage in south Liverpool.

Boris Johnson, mayor of London, also cut his holiday in North America short and was returning overnight. Kit Malthouse, London's deputy mayor of policing, said: "I don't think anybody could have predicted this sort of horrendous spectacle." As the home secretary, Theresa May, broke off her holiday to return to London, she condemned the "sheer criminality" of the violence. Deputy Assistant Commissioner Stephen Kavanagh said one-third more officers were available on Monday nightthan on Sunday, when shops were ransacked and torched in Brixton, south London, and trouble reported in Enfield, Edmonton, Walthamstow and Islington.

Kavanagh vowed to deliver "speedy justice" for Londoners, condemning the waves of looting as "disgusting behaviour, ripping apart people's livelihoods and businesses".

In a bid to contain the trouble , Scotland Yard introduced special powers in four areas – Lambeth, Haringey, Enfield and Waltham Forest, allowing stop and search without reasonable suspicion. The section 60 powers were invoked at midnight on Sunday. One incident of stop and search in Hackney was reportedly the catalyst for violence which erupted in Mare Street shortly after 4pm, and saw local hooded youths battle police.

The Guardian understands senior officers are prepared to add more areas to the list. The special powers have been perceived as targeting certain ethnic groups, thus fuelling tensions.

Meanwhile, the maker of the BlackBerry smartphones, Research in Motion, said it would co-operate with a police investigation into claims its popular BlackBerry Messenger service played a key role in organising the London riots.

Brixton bore the brunt of Sunday's violence. The Lambeth council leader, Steve Reed, said: "We are asking the mayor's office for additional police for tonight and the next few nights." Condemning the "copycat activity", he said: "Somebody described it as gangs of kids doing Supermarket Sweep. It was Curry's where they were after plasma screen TVs, and H&M and Foot Locker where it was clothes and trainers. It wasn't about social issues, it was an opportunity to go on the rob."

Deputy prime minister Nick Clegg, visiting Tottenham, said the violence would leave "big scars" on the community. Surveying the wreckage after the torching of businesses and homes in Tottenham High Road, he spoke to Steve Moore, who lost his jewellery shop in Saturday's violence. "I'm devastated, it's completely gone. My shop just doesn't exist anymore," Moore told him.

Referring to the "copycat" violence across London, Clegg said: "Let's be clear, the violence we saw last night had absolutely nothing to do with the death of Mr Duggan. It was needless, opportunist theft and violence – nothing more, nothing less."

Boris Johnson released a statement describing the scenes of violence and destruction as "utterly appalling".

"I understand the need for urgent answers into the shooting incident that resulted in the death of a young man and I've sought reassurances that the IPCC are doing exactly that," he said. "But, let's be clear – these acts of sheer criminality across London are nothing to do with this incident and must stop now."

Three police officers were taking to hospital after a car was deliberately driven at them in Chingford Mount, Waltham Forest, where a shop was looted on Sunday.

An inquest into Duggan's death was due to open on Tuesday though there seemed to be conflict between Scotland Yard and the IPCC over complaints by his family over "lack of contact" following his shooting.

On behalf of Scotland Yard, Kavanagh said: "I want to apologise to the Duggan family because I think both the IPCC and the Metropolitan police could have managed that family's needs more effectively".

Rachel Cerfontyne, who is in charge of the investigation, said: "Following my meeting with the family yesterday I am very clear that their concerns were not about lack of contact or support from the IPCC. Their concerns were about lack of contact from the police in delivering news of his death to Mark's parents."

She added that "if necessary" the complaint would become part of the IPCC's investigation.