A huge police operation and heavy rain in some areas appear to have prevented a fifth night of disorder.
And magistrates in several cities have been working through the night to deal with those arrested on previous nights.
In Birmingham, a vigil has been held for three men who died after being hit by a car while protecting property.
'Truly dreadful'
The BBC's Jeremy Cooke said the candle-lit vigil for Haroon Jahan, 21, Shahzad Ali, 30, and Abdul Musavir, 31, was attended by some 200 people, and was entirely peaceful.
Harpreet Singh, 28, who helped to organise the vigil, told the crowd: "Let this be a message to other communities, not just Muslims and Sikhs, let's stand together, let's hold candlelight vigils.
"People have been hurt, families have been hurt, if we don't stop this, and the people who are rioting do not stop this, there will be more people dying. It has to stop and we are standing here united."
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At the scene
Jeremy Cooke
BBC News
They gathered on the exact spot on Birmingham's Dudley Road where three young men died when they were hit by a car in the early hours of Wednesday morning.
The 200 or so - mainly Muslim young men - who gathered for the event say the victims were simply trying to protect their property against marauding looters.
Police closed the road but kept a relatively low profile as the event continued. The riot gear - used so many times in recent days - was left inside the police vans pulled up at a discreet distance.
At the scene, mourners laid flowers, lit candles and said prayers in memory of the dead.
Tariq Jahan - whose 21 year-old son Haroon was among those killed - has emerged as a calm voice of authority here. He urged his community to remain peaceful and was heard in an atmosphere of quiet respect.
There is still anger because of what has happened but the prevailing emotion was one of sadness.
Mr Cameron said the deaths were "truly dreadful" and offered his condolences to the men's families.
A 32-year-old man is being questioned on suspicion of murder after the men were run over and killed.
The prime minister will chair a meeting of the government's emergency committee and discuss the violence with cabinet ministers before making a statement on the rioting during an emergency session of parliament on Thursday morning.
He is expected to give details of financial help for people who have lost homes or businesses.
On Wednesday, Mr Cameron said the "fightback" was under way and said said every action would be taken to restore order, with contingency plans for water cannon to be available at 24 hours' notice.
Stolen property
It is the second time in less than a month that MPs have been recalled for an emergency session - the first was for the phone-hacking scandal at the News of the World newspaper.
In other developments:
The father of the three men killed in Birmingham, Tariq Jahan, has appealed for calm
Almost 80,000 people have signed an online petition calling for anyone convicted of taking part in the riots to lose any benefits they receive
Up to 250 officers are sent from Scotland to help colleagues in the Midlands and North of England deal with rioting and disorder
The Met says 16,000 officers were available in London on Wednesday night, and advises people to avoid travel to the areas affected by the disorder
The government launches a website with advice to the public on how to cope with the unrest
Meanwhile, the Met Police has made more than 800 arrests and charged 279 people in connection with violence in the capital.
More than 300 people have been arrested in the West Midlands and a further 100 people have been arrested so far over the trouble in Manchester and Salford.
Courts are sitting through the night in London, Manchester and Solihull in the West Midlands to deal with people arrested during the four nights of disturbances, with those appearing in court mainly facing disorder and burglary charges.
Mr Cameron said anyone convicted of violent disorder would be sent to prison.
Police cuts
A deputation of Labour MPs from London went to the Home Office on Wednesday to demand a "moratorium" on plans to reduce numbers in the Metropolitan Police.
David Cameron: ''We will do whatever is necessary to restore law and order on to our streets''
Labour shadow home secretary Yvette Cooper said: "It is staggering and utterly shameful if it has taken these appalling events for ministers to start waking up to what everyone else has known all along," she said.
"Cutting 16,000 officers - the equivalent of every officer on the streets of London last night - at a time like this is deeply irresponsible."
London's Conservative mayor Boris Johnson has also called for a rethink on police funding but senior government sources say the Treasury will not reopen negotiations on the spending review.
And Home Secretary Theresa May has repeated her belief that police budgets can be reduced without damaging their ability to do their jobs.
But the Home Office said the reductions in the police budget were manageable.
At a press conference, Greater Manchester Police's Assistant Chief Constable Garry Shewan said he had seen "the most sickening scenes" of his career, and said the force had been overwhelmed.
He said the force was "absolutely intent" on bringing the rioters to justice and his officers were already studying CCTV.
The riots first flared on Saturday after a peaceful protest in Tottenham over the fatal shooting of Mark Duggan, 29, by police.
