The man arrested on suspicion of a terror attack in the Swedish capital of Stockholm is reportedly an Isis sympathiser from Uzbekistan.

The 39-year-old allegedly expressed sympathy for the terror group online, according to the Swedish tabloid, Aftonbladet.

A huge police investigation is underway after a lorry ploughed into crowds in a shopping area in central Stockholm, killing at least four people and injuring 15.

Investigators have also arrested a second man in connection with the attack, according to Sweden's national public broadcaster SVT.

Police believe he is connected to the other man who was arrested earlier, the station reported.

Although armed police rushed to the scene shortly after the attack, the driver was able to flee the scene.

Officers later detained a suspect in the suburb of Märsta, around 25 miles north of the city centre.

Police said he "matched exactly" the profile of a man whose image they had earlier released as someone they were searching for.

But they said that while he was "in the vicinity" of the attack but they do not believe he was the driver of the truck.

Nine of those who were hurt in the attack are seriously injured, including one child. Another child is being treated for minor injuries.

Swedish police have released an image of the man they are seeking in connection with the attack

Stefan Lofven, the Swedish Prime Minister, said all evidence pointed to “a terror attack” but vowed that terrorists "will never, ever win".

"These kinds of actions will never succeed", he said. "We know that our enemies are these atrocious murderers and not each other."

"Our message will always be clear: you will not defeat us, you will not govern our lives, you will never, ever win."

In addition to the man in custody, two other people are reported to be helping police with their enquiries.

“I can confirm that we have taken in two people for questioning, but that does not necessary means that they are suspects,” police spokesman Lars Bystrom said.

Victims were covered with blankets while bloodstains could be seen on pavements near the lorry, which was left halfway inside a well-known department store on Drottninggatan (Queens Street), with its cab on fire.

The lorry, which had been hijacked from the Spendrups brewery earlier in the day, hit pedestrians before crashing into Ahlens Mall.

All trains in and out of Stockholm were initially cancelled, although the metro later reopened. The Oresund bridge between Sweden and Denmark was partially closed to limit traffic.

Glen Foran, an Australian tourist in his 40s, told Reuters he saw the lorry coming.

“I turned around and saw a big truck coming towards me,” he said. “It swerved from side to side. It didn't look out of control, it was trying to hit people.”

“It hit people, it was terrible. It hit a pram with a kid in it, demolished it,” he said.

“It took a long time for police to get here. I suppose from their view it was quick, but it felt like forever.”

Another witness told Sweden's Aftonbladet newspaper: “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 from there.”

Witness Jan Granroth told reporters: “We stood inside a shoe store and heard something... and then people started to scream.”

Another witness told the paper they saw hundreds of people “running for their lives” outside the shopping centre.

In pictures: Stockholm truck attack Show all 15 1 /15 In pictures: Stockholm truck attack In pictures: Stockholm truck attack 3 people dead when a truck crashed into Ahlens department store in central Stockholm, Sweden Rex In pictures: Stockholm truck attack People were killed when a truck crashed into department store Ahlens on Drottninggatan, in central Stockholm Reuters In pictures: Stockholm truck attack Special Police forces work at the scene where a truck crashed into the Ahlens department store at Drottninggatan in central Stockholm Getty Images In pictures: Stockholm truck attack Woman is assisted at the scene after a truck crashed into an Ahlens department store in Stockholm Rex In pictures: Stockholm truck attack A policewoman in a gas mask operates at the scene where a truck crashed into the Ahlens department store at Drottninggatan in central Stockholm Getty Images In pictures: Stockholm truck attack People react at the scene where a truck crashed into the Ahlens department store at Drottninggatan in central Stockholm Rex In pictures: Stockholm truck attack Reports say three people have died after a truck crashed into an Ahlens department store in Stockholm Rex In pictures: Stockholm truck attack Armed police operates at the scene where a truck crashed into the Ahlens department store at Drottninggatan in central Stockholm Getty Images In pictures: Stockholm truck attack People react at the scene where a truck crashed into the Ahlens department store at Drottninggatan in central Stockholm Getty Images In pictures: Stockholm truck attack Emergency services close to the scene of an incident in Drottninggatan, a street in the centre of Stockholm, Sweden Lasse Gare/PA Wire In pictures: Stockholm truck attack Passers react at the scene where a truck crashed into the Ahlens department store at Drottninggatan in central Stockholm Getty Images In pictures: Stockholm truck attack People killed in incident when a truck was driven into a department store in central Stockholm Reuters In pictures: Stockholm truck attack Police officers work at the scene where a truck crashed into the Ahlens department store at Drottninggatan in central Stockholm Getty Images In pictures: Stockholm truck attack A general view shows a Ahlens department store after a truck reportedly crashed into it, at Drottninggatan in central Stockholm, Sweden EPA In pictures: Stockholm truck attack A view of a street after a truck reportedly crashed into a department store in central Stockholm, Sweden EPA

Swedish media reports suggested the man in custody was 39 years old and was arrested after a car chase in which his white van was pursued by10 to 15 police vehicles. Some reports suggested he had previously posted pro-Isis messages on his Facebook page.

It is thought that multiple reports of shots having been fired elsewhere in Stockholm were unconnected to the attack.

Swedish PM says Stockholm has been victim of terror attack

The attack comes after lorries were used in terror attacks in Nice and Berlin last year and just two weeks after Muslim convert Khalid Masood ploughed his car into pedestrians on Westminster Bridge in London.

Those atrocities have been linked to Isis but there was no immediate claim of responsibility from the group for the Stockholm attack.