Extra armed police are on UK streets amid a high state of alert following the attack at Manchester Arena.
Arndale Centre in the city was earlier evacuated, with people seen running away screaming and witnesses saying a man was arrested by armed police.
Police said they do not think the arrest was related to the incident at Manchester Arena and the centre has now reopened.
People console each other outside the Arndale
“Security guards and police who were armed shouted at people to get away,” said Sky’s Mike McCarthy, at the scene.
“At least 100 people came round the corner – many of them screaming and trying to get away.”
Some people fell over in the rush to get away and police with sniffer dogs went inside the shopping centre, said McCarthy.
The evacuation happened around 12 hours after a bomb attack killed 22 people at a concert at the arena.
People leave the Arndale Centre after it was evacuated
Following the attack, a suspicious item blown up in Manchester in the early hours.
The controlled explosion took place just after 1.30am in Cathedral Gardens, near the site of the bombing, but it later turned out to be a pile of abandoned clothing.
Another suspicious item sparked an evacuation of London’s Victoria coach station around 6.40am.
Passengers were moved to the end of the street as the area was cordoned off and buses diverted. However, the alert was called off shortly after 8am.
Manchester United players arriving at the team’s Carrington training ground have also had their cars searched.
Security staff used mirrors to check underneath vehicles and opened up the boots.
The team are getting set for Wednesday’s Europa League final against Ajax in Stockholm.
:: Manchester Arena witness: ‘It was absolute carnage’
A “mix of armed and unarmed officers” were called up for the rush hour in London, with Met Police chief Cressida Dick saying they would “continue for as long as is needed”.
Kelly Dixon admits she was one of the lucky ones to find her daughter.
Police Scotland said more armed officers would be at “transport hubs and crowded places”.
Policing in crowded places is also being reviewed in the West Midlands, Norfolk, Suffolk, Bedfordshire, Cambridgeshire, Hertfordshire and Essex.
Extra armed officers were called up in London and other cities after the Westminster attack in March and the Berlin attack in December.
The threat from international terrorism in the UK remains ‘severe’ – as it has been since August 2014 – meaning an attack is highly likely.