A 68-year-old man who was badly beaten after he tried to put out a fire during the recent riots in London has died in hospital, British police said.

Richard Mannington Bowes suffered head injuries in the attack, which took place in the west-London neighbourhood of Ealing on Monday night. He was left in a coma and placed on life support in hospital.

Investigators are treating Bowes' death as a murder, and have identified a suspect on surveillance video they would like to speak with.

The number of people killed in the unrest across Britain has now risen to five, with hundreds of others injured, including many police.

A separate murder investigation is underway in the central city of Birmingham, where three men died after they were struck by car Tuesday night. The three victims were reportedly trying to defend their shops from looters when they were run down.

Police have arrested one suspect in connection with that case.

A 26-year-old man was also killed Monday night during the rioting in London, after he was shot in his car.

British police are using face-recognition software to track down suspects whose images were captured during violent and destructive riots over the past few days.

Scotland Yard recently updated its face-matching technology, just in time for the riots which began on Saturday. The police force is also uploading pictures of suspects to Flickr in an attempt to identify those believed to have participated in criminal activity.

Meanwhile, Prime Minister David Cameron recalled MPs for an emergency session of parliament on Thursday.

Cameron warned rioters and looters they would face harsh consequences for their actions, and said the state would do whatever was necessary to stop the chaos -- possibly even limiting social networking sites being used by rioters to organize.

Cameron also said families living in social housing could be evicted if members are found to have participated in the riots.

"We needed a fightback and a fightback is under way," Cameron said in the televised statement outside his Downing Street office. He said "nothing is off the table" -- including water cannons, which have never been deployed against civilians in mainland Britain.

About 16,000 police patrolled the streets of London again overnight, with many carrying out raids at the homes of suspects. But the capital was relatively quiet for a second consecutive night.

Beginning on Saturday, groups of masked or hooded rioters took to the streets at night, burning buildings, vehicles and storefronts, then looting the contents -- often committing acts of violence in the process.

Police across Britain have made hundreds of arrests in the wake of the riots, and Cameron said police and the courts were being given the tools the needed to deal with the crisis.

"It was a very tough statement," said CTV's London Bureau Chief Tom Kennedy.

"The army hasn't been called in but the government implied that is certainly being held in reserve, that could happen," he added.

The number of Metropolitan Police patrolling the capital's streets was also expected to remain high through the weekend in the hopes of preventing further disturbances. And some courthouses worked through the night to process those who had been charged.

Across most of the U.K. calm prevailed overnight, but there was minor violence in Wales -- the first reported in that country.

The widespread violence -- led mainly by groups of diverse, brazen youths with their faces covered -- has renewed opposition to Cameron's plan to slash 80 billion pounds, or roughly US$130 billion, from public spending by 2015.

Among the spending cuts are massive reductions to police budgets, which could mean as many as 16,000 fewer officers, according to one estimate.

London Mayor Boris Johnson has publicly challenged the cuts, saying the timing is wrong.

"That case was always pretty frail and it has been substantially weakened," he told BBC radio. "This is not a time to think about making substantial cuts in police numbers."

The riots began Saturday during what was supposed to be a peaceful vigil for a dark-skinned man who was shot dead by police in London's Tottenham neighbourhood last week.

The clash quickly grew into a widespread wave of lawlessness that appeared to have little connection to the original incident.

With files from The Associated Press