At least four people have been injured, one of them seriously, after a knifeman attacked shoppers in Manchester’s Arndale shopping centre.

Counter-terrorism detectives are investigating after the victims were stabbed in the city centre complex late on Friday morning. A man in his 40s was initially detained on suspicion of serious assault but he was later arrested on suspicion of terrorism.

Witnesses described a scene of terror as shoppers, some of them wounded, sought refuge in stores as the attacker ran amok just before 11.15am.

One shop worker, who gave his name only as Jordan, said: “A man was running around with a knife lunging at multiple people, one of which came into my store visibly shaken with a small graze.

“Soon after, security staff told all retail staff to close their doors and move the public to the back of the stores.”

Great Manchester Police initially said five people had been stabbed, but later amended the number of victims to four. North West Ambulance Service said all had been taken to hospital by paramedics.

Manchester Arndale stabbings: Shopping centre attack in photos Show all 10 1 /10 Manchester Arndale stabbings: Shopping centre attack in photos Manchester Arndale stabbings: Shopping centre attack in photos A police officer points a taser while the other holds a man down outside Arndale shopping centre Five people have been injured in a series of stabbings at Manchester’s Arndale shopping centre. Footage posted on Twitter showed a police pointing a Taser at a man lying face down on the pavement outside the shopping centre as another officer handcuffed him. John Greenhalgh/Twitter Manchester Arndale stabbings: Shopping centre attack in photos Police running through the Arndale Centre Greater Manchester Police said counter-terrorism detectives were investigating the attacks at the city centre complex on Friday morning. A man in his 40s has been arrested on suspicion of serious assault. GrizzleMarine/PA Manchester Arndale stabbings: Shopping centre attack in photos Armed police officers outside the Arndale Centre Paramedics have treated four people, a spokeswoman for North West Ambulance Service (NWAS) told The Independent. No details on the victims' conditions were immediately available. PA Manchester Arndale stabbings: Shopping centre attack in photos Police running through the Arndale Centre The Arndale centre has been evacuated. GrizzleMarine/PA Manchester Arndale stabbings: Shopping centre attack in photos Police cordoned off the outside the Arndale Centre PA Manchester Arndale stabbings: Shopping centre attack in photos A police helicopter flies above the Arndale Centre PA Manchester Arndale stabbings: Shopping centre attack in photos Ambulances parked outside the centre PA Manchester Arndale stabbings: Shopping centre attack in photos Police surround Arndale shopping centre Getty Images Manchester Arndale stabbings: Shopping centre attack in photos Paramedics outside PA Manchester Arndale stabbings: Shopping centre attack in photos MANCHESTER, ENGLAND - OCTOBER 11: Police surround Arndale shopping centre, where a man allegedly stabbed five people on October 11, 2019 in Manchester, England. A man in his 40s was arrested on suspicion of assault, as paramedics treated five people for stab wounds at Manchester Arndale, a large shopping complex in the city centre. (Photo by Anthony Devlin/Getty Images) Anthony Devlin Getty Images

Footage posted on Twitter appears to show the moment police detained the suspect, who is seen lying face down on the pavement outside the shopping centre as he is handcuffed. Another officer is shown pointing a taser at the man.

A GMP spokeswoman said: “Specialist officers are continuing to respond to an incident at the Arndale shopping centre in Manchester city centre.

“In these early stages we are keeping an open mind about the motivation of this terrible incident and the circumstances as we know them.

“Given the location of the incident and its nature officers from Counter Terrorism Police North West are leading the investigation as we determine the circumstances.

“A man in his 40s – who was arrested at the scene on suspicion of serious assault – remains in custody for questioning.”

The force could not confirm whether officers were looking for anyone else in connection to the attacks, but Greater Manchester’s deputy mayor for policing said “the scene has been secured”.

Police said two women, one aged 19, were taken to hospital with stab wounds and were in a stable condition. A 50-year-old man was also taken to hospital after being stabbed. No details on his condition were given.

A fourth victim, a woman in her 40s who was not stabbed, was assessed by paramedics but did not need to go to hospital.

A photograph sent to the Manchester Evening News appeared to show a bloodied victim surrounded by paramedics at a Starbucks coffee in the Arndale, with screens erected to shield them from public view.

One witness told the newspaper they had seen the knifeman “running around going for as many people as possible”.

Freddie Houlder, 22, said he had been in the shoe shop Office when a woman was knifed “10 metres away”. He added: “Luckily she had quite a thick jacket – she thought originally it was a fake knife because of how easily it grazed off but police came in and said it was a real knife and she burst in to tears.

“I definitely don’t think it was gang violence because this guy was going around trying to stab random people.”

Police outside the Arndale Centre in Manchester after four people were stabbed in “random” attacks (PA)

The Arndale was evacuated following the attacks and the area around the centre has been cordoned off by police.

Tina Concar, 52, who was among those evacuated, said: “We only knew something was unfolding as loads of people started running towards us, at first shouting ‘bomb’.

“But then someone mentioned that a person had been stabbed. People were panicking and running as security staff were running the other way.”

Boris Johnson, the prime minister, said he was “shocked by the incident in Manchester and my thoughts are with the injured and all those affected”.

Lucy Powell, the Labour MP for Manchester Central, tweeted: “Terrible news coming from the Arndale today. Thoughts are with all those caught up in it and with our frontline services dealing with it.”

Home secretary Priti Patel said she was “very concerned by the incident in Manchester”, adding: “I am, as always, very grateful to the police for running towards danger to keep us safe. Now important they are given space to carry out their investigation.”

The Arndale Centre is just a few hundred yards from Manchester Arena and Victoria railway station, both of which have been the scene of recent terror attacks.

Twenty-two people, the youngest just eight years old, were killed in May 2017 when Salman Abedi detonated a suicide bomb in the arena following an Ariane Grande concert.