Media playback is unsupported on your device Media caption Boris Johnson meets angry residents in Clapham Junction

A 21-year-old man has been arrested on suspicion of starting a massive fire at a furniture store in Croydon.

The family-run House of Reeves business was destroyed on a third night of violence in London on Monday evening.

Up to 16,000 police officers are patrolling London's streets to prevent further rioting, while a man shot during riots in Croydon has died.

A total of 685 arrests have been made and 111 people charged after three nights of riots and looting.

Much of London shut down early on Tuesday amid fears of a fourth night of violence.

The Metropolitan Police's Operation Trident began an investigation after a man was found in a car with bullet wounds to the head in Warrington Road at 21:15 BST on Monday.

Police said the 26-year-old man was involved in a car chase and shot following an altercation with a group of about nine men. Two men have been arrested and bailed over the death.

There was a stand-off at Feltham young offenders institution, in west London, when some inmates refused to leave the gym.

The Ministry of Justice said trained officers were deployed and the situation had been resolved by 00:30 BST. No injuries were reported to staff or prisoners.

The Met described the riots on Monday night as the worst in recent years.

'Spirit of London'

Since Saturday 111 officers have been injured, some seriously, the Met said. Five police dogs have also been injured in the violence.

Officers from some 30 forces across the country have been sent to the capital to support the Met.

The additional officers, including community support officers, were made available from noon on Tuesday until Wednesday morning.

Earlier, windows of three stores near Sloane Square Tube station in west London were smashed by rioters.

Several arrests have been made in Canning Town, east London, after skirmishes between youths and police in Prince Regent Lane.

Media playback is unsupported on your device Media caption David Cameron visited Croydon to see the damage caused in Monday's riots

Meanwhile a BBC producer has reported 100 young men standing in Church Street, Enfield, north London, have vowed to "defend the streets".

And about 300 people have gathered in Southall, west London, intent on protecting religious buildings and businesses.

The Met has also urged parents to keep their children at home as Deputy Assistant Commissioner Stephen Kavanagh said the force was thinking about the use of plastic bullets.

However he said the force was "not going to throw 180 years of policing with the community away".

"The use of any tactics will be considered carefully," he said. "That does not mean we are scared of using any tactic."

Meanwhile, a crowd of more than 100 surrounded London Mayor Boris Johnson - who returned from holiday early due to the troubles - at Clapham Junction and several residents questioned him about the lack of officers to protect them from marauding rioters.

At one point the crowd started chanting: "Where's our mayor?"

Mr Johnson picked up a broom and praised the community for helping with the clear-up saying it showed the "spirit of London".

'Sickening' disorder

He told people whose businesses were attacked that he was sorry for their loss and added that looters would "face punishments they will bitterly regret".

Prime Minister David Cameron, who visited Croydon following Monday's riots, described the scenes of disorder as "sickening".

He is due to chair another meeting of the emergency committee Cobra at 09:00 BST on Wednesday.

Met officers said they hoped they were wrong but the force was "preparing for mass disorder again".

A number of shops across London shut early on Tuesday, including shopping centres in Wimbledon, Putney, Rotherhithe and Wandsworth.

And the National Maritime Museum in Greenwich, south London, closed early while businesses in the area were urged to shut on Tuesday afternoon.

Image caption The House of Reeves furniture store was set alight on Monday

The Met also released 15 CCTV images showing looting in Croydon and Norwood Road and has created a dedicated website showing the images.

On Monday evening disorder began in Hackney and spread to Croydon, Clapham, Camden, Lewisham, Peckham, Newham, East Ham, Enfield, Woolwich, Ealing and Colliers Wood.

About 6,000 police officers were on duty, including officers from neighbouring forces.

The trouble began after police shot a man dead in Tottenham.

A peaceful protest in Tottenham on Saturday over the fatal shooting by police of Mark Duggan, 29, was followed by violence which spread into Sunday.

An Independent Police Complaints Commission (IPCC) investigation into the death showed no evidence Mr Duggan opened fire at police officers before he was shot.

An inquest heard Mr Duggan was shot dead by a single bullet wound to the chest.

His family released a statement which said they were "deeply distressed by the disorder affecting so many communities across the country".