The incident is believed to have happened at the Kingsbury Halal Butchers just 100 yards from Kingsbury Tube station and in a busy shopping street.

A Scotland Yard spokesman said: ‘Police were called at approximately 8.40am to a disturbance in Kingsbury Road, Kingsbury.

Crime scene: The multiple stabbing is believed to have taken place at Kingsbury Halal Butchers

Cordoned off: Metropolitan Police officers at the scene of the attack, with a paramedic's kit visible in the foreground

‘Officers attended and attempted to speak with a man, who subsequently attacked them.

‘Four officers were injured during the incident and have been taken to hospital.

‘A man has been arrested on suspicion of attempted murder and remains in custody at a north London police station.’

A Metropolitan Police spokesman confirmed to MailOnline that all four officers are in a stable condition.

One sustained a stab wound to the stomach, another sustained head injuries and a stab wound to the arm, a third was wounded in the leg while a fourth suffered a broken hand.

Further down from Kingsbury Halal Butchers on the other side of the roundabout Ketan Vyas, the manager of the VB and Sons cash-and-carry store, described how a man aged 30 to 40 had burst into his shop chased by police.

Shock: The attack happened in broad daylight on a busy shopping street

Stabbing: The area has been sealed off by police, with one man arrested on suspicion of attempted murder

He went on: 'He picked up some cans of beans and threw them at the police and then carried on running out of the store and down the road.

'There were a lot of police after him. He was only in here for a few seconds. Fortunately no staff were harmed.'

Shopkeeper Girish Modha said: 'A man was shouting at police in a small alleyway next to a hairdresser's shop which neighbours mine.

'He grabbed a piece of fluorescent tubing and brandished it at police. He then ran down Kingsbury Road, going into a cash-and-carry shop. At one point I think he threw a brick and smashed a police car window.

'He then ran round the roundabout and carried on towards the Tube station. He went into a butcher's, got a knife and that's when the stabbing took place.'

A worker at a Carphone Warehouse store opposite the butcher's said: 'After the incident I saw about eight police officers on top of a man. Ambulances arrived to take away the injured policemen and the man was also taken away.'

Sky's Martin Brunt tweeted that one of the officers was stabbed in the stomach and that the attacker went 'berserk'. 

Eyewitnesses told Bottr that police were called after a man began to attack people 'randomly' .

Brunt added that the suspect had been shouting in the street in 'quite a disturbed way', which led to 999 calls being made.

The Kingsbury Roundabout in north London where the incident happened

Injured: Four police officers have been taken to hospital to be treated for knife wounds, according to Scotland Yard, after being attacked at Kingsbury roundabout

Olympia Logofagul, 24, who works at the Kings Coffee shop on Kingsbury Road, said: 'I was working and I saw some police officers standing outside.

'There were a lot of officers, more than five but no more than 10.'

A spokeswoman for London Ambulance Service said they took five patients to hospital, all conscious and breathing.

She said: 'We were called at 8.50 this morning to an incident in Kingsbury Road.

'We sent two single responders in cars, four ambulance crews and a duty officer.

'We treated five patients, they were all conscious and breathing, and they were taken to hospital.'

Kingsbury Road - a busy thoroughfare in north-west London and normally jammed with shoppers on a Saturday morning - was deserted either side of the roundabout, with police having blocked off the road in both directions.

The hairdressers, Mr Modha's sweet shop and a chemist were cordoned off.

There are 30 police cars and 15 ambulances attended

Mr Duggan, 29, was shot by police officers a week ago in Ferry Lane, as officers attempted to make an arrest.

Post-mortem tests found he died from a single bullet wound to the chest.

Officials from the Independent Police Complaints Commission are in Tottenham talking to people to gather more information.

Violence began in Tottenham on Saturday after the fatal shooting by police of Mark Duggan.

The riots then spread to other parts of London and other cities in England.

Further tests
Investigations by the Independent Police Complaints Commission (IPCC) show two shots were fired by a Scotland Yard CO19 firearms officer.

But the police watchdog said there was no evidence Mr Duggan had fired at police.

The IPCC said ballistic tests showed "no evidence that the handgun found at the scene was fired".

Further tests are being conducted on the illegal firearm, which was converted from a blank-firing pistol to one that shoots live rounds, the IPCC said.

A spokeswoman for the Duggan family said one of the options being considered was to request a second post-mortem examination.

Witness boards
In order to try and speak to as many witnesses as possible, IPCC investigators will be stopping and talking to commuters, handing out information leaflets and putting up witness boards and posters.

IPCC Commissioner Rachel Cerfontyne said: "It is one week since Mark Duggan died on Ferry Lane.

"It is a busy road and there is a busy Tube and train station just minutes away.

"I want to appeal directly to anyone who saw or heard anything that may assist us with our investigation - or if you know anyone who has any information and has yet to come forward and speak to us, please urge them to do so."

The inquest into Mr Duggan's death was opened at North London Coroner's Court in High Barnet on 9 August and adjourned until 12 December.