A firearm has reportedly been discharged at a police officer in Birmingham after rioting and looting spread to Manchester, Salford, Liverpool and the Midlands.
:: Reports: Firearm discharged at police officer in Aston in Birmingham.
:: Police numbers almost treble in London.
:: Met Police considers issuing officers with plastic bullets (baton rounds).
:: "No evidence" Mark Duggan fired at police before his death.
:: Police station in Nottingham is firebombed by a gang of 30-40 men.
In Manchester city centre, hundreds of youths went on the rampage, leading to running battles with riot police. Officers called the violence "unprecedented" and "senseless".
The vandals threw stones and other missiles at shop windows, and broke into stores.
Rioters set fire to a Miss Selfridge shop on Market Street - and at least 47 people were arrested over the trouble in Manchester and Salford.
Around 100 youths also looted Foot Asylum in Manchester's Arndale Centre after two raiders smashed open the glass entrance with a large stone slab.
Hundreds of riot police had tried to move crowds who had gathered on Piccadilly Gardens, leading to running battles with youngsters wearing masks and hoods.
Around 200 missile-throwing youths gathered in the south Liverpool area of Toxteth causing disorder and damage, Merseyside Police said.
In Salford, protesters threw rocks at police in riot gear and at least one vehicle was on fire. Up to 200 youths were in a stand-off with police around the shopping precinct.
In Wolverhampton, some stores were broken into, and in West Bromwich, two cars have been set on fire.
Later, West Midlands Police said the situation was under control in West Bromwich and a large crowd had dispersed. At least 80 people were arrested across the region.
Shops were targeted in Birmingham, although two groups of youths were largely kept away from the city centre by riot police.
A police station in Nottingham was firebombed by a group of 30 to 40 men. No injuries were reported and at least eight people were arrested in connection with the attack.
Meanwhile, around 16,000 police officers - nearly treble the number the previous night - have been on patrol in the capital to try to prevent a fourth night of rioting and looting.
During the evening, the situation appeared relatively calm, with a handful of arrests reported in the Canning Town area of east London.
But in Enfield, north London, a group of 50-70 local men have been patrolling the streets to try to stop disorder.
One of the group spoke to Sky News correspondent Tom Parmenter.
Nick Davidson said: "We've had enough of police just standing there while people are looting and ruining the whole area.
"Everybody here pays taxes and have had enough of it. We're sickened by police doing absolutely doing nothing."
He denied that the group was antagonising the situation, adding "nobody has done anything wrong.
"If anybody saw any people looting we would be taking action but the police have not done and that is why we are here."
Also in Southall, dozens of Sikh men have been standing outside a temple and patrolling the local streets to help protect the community.
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After police were vastly outnumbered in London on Monday night with just 6,000 officers on patrol amid "sickening" scenes of violence, the Prime Minister announced the increase in numbers in Downing Street.
Scotland Yard says officers have made 685 arrests and charged at least 105 people over the disorder which began in London on Saturday night.
A man has been arrested over an arson attack which destroyed a furniture store in Croydon on Monday night.
All police cells in London were full and anyone arrested now was being taken to surrounding areas.
Police have also released pictures of looting suspects.
A total of 111 officers and five police dogs have been injured during escalating riots in the capital.
All Metropolitan Police leave has been cancelled and special constables have been asked to work.
Reinforcements are being provided by 26, or 60%, of the country's other forces, and the Met has called on retired officers to help out.
Sky's crime correspondent Martin Brunt said the Met was considering a change of tactics and that officers may even be issued with plastic bullets.
Brunt said: "Police have promised to swamp the streets and act tougher if there's another night of rioting in the capital.
"A change in tactics could include the use of plastic bullets (baton rounds) to clear looters and vandals.
"Such a weapon has been available to police in the past three nights, but commanders have resisted using them."
Meanwhile, the Met is carrying out its biggest ever criminal operation after three nights during which groups of youths burned buildings and cars on the capital's streets.
The unrest on Saturday night in Tottenham was said to have been sparked by the fatal shooting by police of local man Mark Duggan.
There was reportedly an exchange of fire with police before his death.
But there is no evidence Mr Duggan opened fire at officers before he was shot dead, ballistic test results obtained by the Independent Police Complaints Commission said.
On Monday night, Croydon, Clapham, Ealing, Hackney, Peckham and Enfield were among the areas of London worst hit by the disorder.
There was also trouble in other English cities, including Bristol, Birmingham and Liverpool.
Prime Minister David Cameron flew back from holiday early as the violence escalated and has announced that Parliament will be recalled on Thursday.
He will chair another meeting of the Government's emergency Cobra committee at 9am on Wednesday.
Brunt said there were 500 detectives working to identify vandals who have not been arrested so far. The investigation is bigger even than the one for the 7/7 bombings.
A 26-year-old man has died after being shot in Croydon, south London, on Monday night and another man in his 60s is in a critical condition after being attacked in Ealing, west London.
Mr Cameron described the violence as "criminality pure and simple" and said the Government would do "everything necessary to restore order to Britain's streets and to make them safe for the law-abiding".
He warned those involved in the trouble they were not only risking their own communities, but their own futures, adding: "If you are old enough to commit these crimes you are old enough to face the punishment."
Much of the rioting appears to have been coordinated through messages on Facebook, Twitter and Blackberry messenging service called BBM .
Tottenham MP David Lammy has called for Blackberry to suspend its BBM service to stop rioters from being able to communicate.
Strathclyde Police have arrested a 16-year-old in Glasgow in connection with a Facebook message allegedly inciting others to riot.
And two 18-year-olds have been arrested in Folkestone for allegedly inciting rioters through social media sites.
Wednesday's international football friendly between England and Holland at Wembley has also been cancelled due to security fears.
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