A SUSPECTED terrorist deliberately drove at young children, sending prams flying as a stolen beer truck sped through a crowded shopping street in Stockholm, witnesses have said.

Authorities have now confirmed that the suspect, a 39-year-old Uzbekistan-born man, had been on their radar for some time before the truck was high-jacked and used to plough through terrified crowds, killing four people and leaving 15 people, including two children, injured.

65 Shocking footage shows the moment the truck ploughed through crowds in Stockholm Credit: Laserfilm

65 People rush to help the wounded after the horrific attack that saw a stolen lorry plough through crowds in Stockholm Credit: Rex Features

65 The truck, taken from the scene overnight, was seen charred after crashing into the department store Credit: AP:Associated Press

65 Four people are believed to have been killed in the attack with reports of many more wounded Credit: Rex Features

65 Police block off the horrifying scene of the attack shielding bodies from view as a manhunt is launched Credit: Getty Images

65 A photograph of man being hunted by police in connection with the horror that unfolded in Sweden's capital

65 A medic walks through the streets, surrounded by the covered bodies of victims from the horrifying attack Credit: Rex Features

65 A truck has hit pedestrians in Sweden's capital of Stockholm with witnesses running for their lives

65 The truck involved in the attack was towed away from the scene overnight Credit: Getty Images

65 Witnesses ran for their lives after the horrific crash on a busy shopping street in Stockholm

65 Passers-by flee the scene of the attack, which saw a truck rammed into a shopping centre in Stockholm Credit: PA:Press Association Images

65 A woman is reduced to tears after the crash with authorities now saying it was terrorist attack Credit: Getty Images

65 Crown Princess Victoria and Prince Daniel visit the scene with the princess reduced to tears Credit: Rex Features

Local media reported that a homemade bomb had been found in the 30-tonne truck with the head of Sweden's National Police Dan Eliason confirming a "bomb or incendiary object" had been discovered.

Mr Eliason said: "We have found something in the truck, in the driver's seat, a technical device that should not be there.

"I cannot say at this stage that this is a bomb or some sort of flammable material.

"Whether it is a classic bomb or a fire device or something else is subject to technical analysis."

The vehicle was last night towed from the scene, with photographs showing the charred front after it crashed into the high end department store.

As emergency services work today to clean the streets left bloodied by the attack, the head of Sweden's domestic intelligence agency Anders Thornberg revealed authorities had previously been aware of the man, saying: "The suspect didn't appear in our recent files but he earlier has been in our files."

65 How the terror attack unfolded on Friday afternoon

Authorities said they were confident they had nabbed the right man, with reports surfacing from Sweden that the man, a father-of-four, had posted jihadist propaganda on his Facebook page and had "liked" images of people injured in the Boston Marathon explosion in April 2013.

Authorities added man arrested was the driver of the vehicle, and matched CCTV images released in the immediate aftermath of the attack.

They said he may have been injured in the attack with the bomb inside the truck possibly going off while he was still inside the vehicle.

Local media Aftonbladet reported the man was arrested after witnesses spotted him, recognising him from the photograph released by authorities.

Mr Thornberg said the security services are working with other nations' security agencies on the matter, but declined to elaborate.

He said that investigators were unsure whether others had been involved in the attack, saying they could not exclude that fear.

Photographs showed another man being led away by authorities but police have not confirmed any further arrests.

Sweden's security service said this morning they have launched a broad investigation into the incident, saying: "We have been working every minute since the incident are working tirelessly.

"The focus is now both to find out who the perpetrators are and to ensure that no more attacks occur."

65 Forensic workers examine the scene, with blood left across the street Credit: Getty Images

65 Forensics are just one part of the investigation with police also examining whether the man had worked alone or with anyone else Credit: Getty Images

65 Armed police have remained at the scene with Sweden increasing ins security in the wake of the attack Credit: EPA

Eyewitnesses yesterday tearfully recounted the attack, saying the truck had travelled for more than 500 yards along a main pedestrian street known as the Drottninggatan before it smashed into a crowd outside the upmarket Ahlens department store, killing four and leaving 15 injured, including ten seriously.

It is believed the attacker jumped from the hijacked beer lorry after the attack and fled through the carnage, with the Prime Minister Stefan Lofven saying all signs pointed to a "deliberate" terror attack on Sweden's capital.

He has since announced plans to strengthen border controls in the wake of the crash that happened just before 3pm local time yesterday.

Flags are today at half mast as devastated crowds have descended to lay flowers at the bloody scene.

The horrific scenes in Stockholm come just weeks after five innocent victims were killed when a car ploughed through crowds on Westminster Bridge, outside the Houses of Parliament.

Investigators will now investigate if suspects have links to terror groups, including ISIS.

65 People can be seen fleeing the street as a truck hit terrified shoppers before ploughing into a shopping centre Credit: Laserfilm

65 The truck ploughed into a shopping centre after it crashed through crowds on a Stockholm street Credit: Reuters

65 Flowers have been left near blood stains at the scene, with Crown Princess Victoria visiting the scene Credit: Getty Images

65 Messages to the victims were left at the scene, wishing that they would rest in peace Credit: Getty Images

65 Part of the truck's side had been cut away before it was towed away Credit: Getty Images

65 A street sign was knocked down in the chaos that unfolded in the city centre Credit: AP:Associated Press

65 A medic runs through the scene of carnage as victims of the attack are treated by the emergency services Credit: Rex Features

65 Police appear to place a man in handcuffs after a reported raid following the attack - there is no indication this man was the driver Credit: Splash News

65 A man stands with his head against a pillar as he is handcuffed by police in the aftermath of the attack Credit: Sky News

65 Officers can be seen holding a person down to the ground just after the truck crashed into a department store Credit: Aftonbalet

Details around how the terror attack unfolded have emerged with it understood that the beer truck used in the attack had been stolen as its original driver was unloading it at a restaurant.

Earlier two people were taken in for questioning in connection with the deadly attack, although it has not confirmed if they are suspects.

Senior cop Mats Lofving has warned people to be cautious.

He said: "We don't know whether this incident is isolated or whether we can expect more.

"We have police positioned at several strategic places with a particular risk threat."

Initial reports suggested at least five people were killed in the attack but as more information emerged from local authorities the death toll was reduced to four.

Stockholm City Council has said 15 people, including children, were treated in hospital.

A Downing Street spokeswoman today said: "The Prime Minister called Prime Minister Lofven of Sweden today, to express her condolences and those of the British people for the terrible attack that took place in Stockholm yesterday.

"She was clear that the UK stands firmly by Sweden's side, and they agreed on the importance of working together to tackle these threats, which we all continue to face."

Floral tributes have been placed at the site, with Sweden's Crown Princess Victoria breaking down in tears as she visited the bloodied streets.

She said: "Swedish society is built on tremendous trust and community. We will go stronger out of this in some way."

65 Emergency services rushed to the scene at about 3pm local time after the truck ploughed through crowds Credit: Rex Features

65 Swedish Prime Minister Stefan Lofven lays flowers at a makeshift memorial near the scene Credit: Getty Images

65 A huge wall of flowers have been placed at the scene as members of the public pay tribute to those killed Credit: Getty Images

65 Streams of people were seen running from the shopping street fleeing the carnage of the attack Credit: Twitter/@johnnychadda

65 A person can be seen held on the ground by officers, with one seen holding his gun in its holster

65 Emergency crews are at the scene with witnesses saying they had run for their lives as the attack unfolded Credit: Twitter/@johnnychadda

65 The truck smashed into a department store on Friday afternoon, leaving at least four dead Credit: Aftonbladet

65 Thick black smoke could be seen rising from the scene of the smash in the Swedish capital as emergency services patrolled Credit: Getty Images

65 A man can be seen with police after the attack, as officials announce two people are being quizzed by cops

65 Officers wore gas masks as they rushed to the scene as black smoke was seen pouring from the truck used in the attack Credit: Getty Images

65 A police officer helps a woman cross a road in the aftermath of the terror attack as locals opened their homes to the stranded Credit: Twitter / @Frisund

Horrified witnesses said a pram was hurled into the air as desperate pedestrians ran for their lives as the lorry crushed everything in its path.

Another told of bodies and blood "everywhere" and even a dead dog with its owner screaming beside it.

Local news site Expressen reported that the driver of the truck escaped the scene, with witnesses describing a "lone man" who put a balaclava over his face before he drove the truck into crowds of people.

Sky News reported that the suspect is believed to have run towards the underground station as smoke billowed out of the crashed vehicle.

A witness, Anna told local Aftonbladet news that she saw "hundreds" of people running for their lives.

She said: "I saw hundreds of people run, they ran for their lives. I turned and ran as well."

On Friday evening Prime Minister Lofven laid a bouquet of red roses and lit a candle near the scene of the atrocity.

He had earlier said the country was in a "state of shock" adding "the aim of terrorism is to undermine democracy. But such a goal will never be achieved in Sweden."

65 Shocking footage shows the moments shoppers run for cover into a clothing store in Stockholm Credit: VG TV

65 A second after the shoppers dashed into the shop a truck was seen speeding past the shop Credit: VG TV

65 Sweden's Prime Minister Stefan Lofven places flowers and a candle where a hijacked beer truck ploughed into pedestrians Credit: AP:Associated Press

65 Prime Minister Stefan Lofven sheds a tear as he visits the site of the atrocity in Stockholm Credit: Getty Images

65 Sweden's Prime Minister Stefan Lofven places flowers at Queens Street Credit: Reuters

65 National Police Commissioner, Dan Eliasson, Swedish Security Service and Mats Lofving hold a news conference Credit: Reuters

65 Stockholm is on lockdown following the attack with police warning people not to come to the city centre Credit: Getty Images

65 People huddled together in the wake of the horrific attack that claimed the lives of several people Credit: EPA

65 A woman cries as she walks through the streets of the city's capital in the aftermath of the atrocity Credit: Rex Features

65 Emergency services work at the scene where a truck crashed into the Ahlens department store at Drottninggatan in central Stockholm Credit: Getty Images

Another witness Dimitris told Aftonbladet news: "I went to the main street when a big truck came out of nowhere.

"I could not see if anyone was driving it but it got out of control. I saw at least two being run over.

"I ran as fast as I could."

Annevi Peterson described people lying dead and injured in the street with blood everywhere.

She told BBC News: "I heard the noise, I heard the screams, I saw the people.

"There was, just outside the store, there was a dead dog, the owner screaming, there was a lady lying with a severed foot. "There was blood everywhere, there were bodies on the ground everywhere.

"There was a sense of panic, people standing by their loved ones but also people running away."

65 Tracks of blood near the scene contrast with the flowers left for those killed and injured in the terror attack Credit: Getty Images

65 Armed officers remained at the scene on Saturday morning Credit: Reuters

65 A family stands near the scene after authorities confirmed they were doing everything possible to investigate the attack Credit: Getty Images

Pools of blood were visible on the street along with bodies covered in blankets.

Paramedics could also be seen tending to the injured near the truck.

Jan Granroth told Aftonbladet: "We stood inside a shoe store and heard something ... and then people started to scream. "I looked out of the store and saw a big truck."

In the aftermath of the attack images of a number of people being held down by police officers emerged from the scene - but cops have confirmed only one arrest.

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Footage of the scene showed streams of people hurry down the main street, while video footage revealed terrified shoppers dived into shops seconds before the truck raced past.

Photographer Annevi Petersson said: "I was in a store at Drootninggatan where the truck passed by. Had just stepped into a fitting room, heard the noise and the screams, ran out and people laying on the street.

"I saw a woman had a partly severed foot. People screaming in panic, others ran. I saw people laying bloody on the street and got out of there."

People have since started to open up their homes and businesses to those trapped by the terror attack, using the message #openstockholm on social media.

Shots were also reported near Fridhemsplan, about 20 minutes from the crash site, but no links with this and the attack have emerged.

Chaotic scenes: Brit tourist describes the terrifying 'terror' attack A British tourist on holiday in Stockholm has described seeing "lifeless bodies" covered with towels at the scene of the suspected terror attack. Reporter Harriet Rose-Gale, 26, was eating lunch metres away from the spot where a truck ploughed into pedestrians in the Swedish capital. Harriet, of Marlborough, Wilts., described scenes of panic as dozens of emergency vehicles flooded the streets. She said: "We were literally 100 or 200m away having lunch when a couple of police cars went by followed by about 20-30 emergency vehicles continuously. "I walked up the road and we could just see a lorry, a truck, and what we could only assume was a lifeless body in front of it. "It had a peach or orange towel covering it and there was another body with a white sheet in the middle of the road. "There were armed police running past us and shouting in Swedish. I don't know what they were saying. "The police officer said to just keep walking. They are sending people away from the scene. "It seems to be a shopping street. There are lots of restaurants and shops near it. It's right next to our hotel, which is where we were walking. "We were trying to find out what happened but there was so much panic because of what's just happened in London. Everyone is on high alert. "There were crowds of people flooding along the street to get away and lots of police officers with guns and lots and lots of sirens. "There has been a few people walking past with blankets and there is a big cordon around the street. "Everyone was just trying to figure out what was going on. "I'm not sure what we are going to do but I feel quite safe. There are lots of police around and they are diverting people away from the area."

Yesterday, London's Mayor Saiq Khan, who had just weeks ago spoken out against terror attacks in the wake of the Westminster horror, said: "My thoughts and deepest sympathies are with the victims and the families who have been affected by the horrific attack in Stockholm (on Friday).

"The full details are still emerging, but once again it looks like we have seen a despicable act of terrorism aimed at harming innocent people and attacking our shared values of democracy, freedom, justice and tolerance.

"Londoners know how it feels to suffer from senseless and cowardly terrorism. And I know we share a steely determination with the people of Stockholm that we will never allow terrorists to succeed.

"We will never be cowed by terrorism, and today - London stands united with Stockholm and Londoners stand with the people of Stockholm."

65 An officer is seen in Hjulsta suburb in Stockholm Credit: Reuters

65 Flowers have been left at the scene of the attack that left Sweden reeling Credit: AP:Associated Press

65 A woman stands on the street holding flowers as a tribute to those killed in the attack Credit: AP:Associated Press

65 Members of the public were reduced to tears visiting the site the morning after the attack Credit: AP:Associated Press

65 A heavily armed officer can be seen walking through the streets of Stockholm as the city was placed on lockdown Credit: Reuters

65 A group can be seen huddled around a person on the ground as many are reported to have been injured Credit: Rex Features

65 Armed cops guard Stockholm castle in the aftermath of the terror attack as security is increased in the area Credit: AP:Associated Press

65 Swedish Prime Minister Stefan Loefven makes a statement after a truck reportedly crashed into a department store in central Stockholm, Sweden Credit: Getty Images

65 The Prime Minister has confirmed that all signs suggest the atrocity was 'deliberate' terror attack Credit: AP:Associated Press

65 Officers can be seen on the streets, having been called to the city centre just before 3pm local time on Friday Credit: EPA

65 The horrific aftermath saw injured people pulled from the street and helped by shocked bystanders and authorities Credit: Rex Features

65 People have been warned to stay away from the city centre in the aftermath of Friday's atrocity as transport networks are locked down Credit: Getty Images

65 Local police descended on the scene, warning members of the public to stay away from the city centre Credit: AP:Associated Press

65 People were seen running for their lives after the truck ploughed through crowds in a busy Stockholm shopping street Credit: Twitter/@johnnychadda

It has been announced that police in Norway's largest cities and at Oslo's airport will be carrying weapons until further notice.

Police officers in Norway, which borders Sweden, do not usually carry guns.

In Finland, police increased patrols in the capital Helsinki.

The response follows a series of attacks in Europe by terrorists using vehicles as weapons.

The worst attack was last year in France on the Bastille Day national holiday of July 14, in which a man rammed a truck into a crowd in the Mediterranean resort of Nice, killing 86 people.

He was shot dead by police, and the Islamic State group claimed responsibility.

Last month, Khalid Masood, a 52-year-old convert to Islam known to British security services, drove a car at high speed into pedestrians on London's Westminster Bridge before launching a frenzied knife attack on a policeman guarding the parliament building.

The incident killed five people, while Masood himself was shot dead by police.

Last November, eleven were injured when Abdul Razak Ali Artan, 18, drove into pedestrians at Ohio State University and stabbed people before a cop shot him dead.

Just one month later, a man hijacked a truck and slammed into shoppers at a Christmas market in Berlin, killing 12 people.

That attacker was shot dead by police in Milan four days later, and the rampage was claimed by the ISIS.