Shop assistants were left "terrified" after a man they refused to serve dropped a gun to the floor while he argued with them.

Staff at the Tesco Express, in the centre of Norwich, told the man they would not serve him because he did not have ID.

They said he became argumentative and aggressive and during the row, he accidentally dropped a handgun to the floor of the shop.

He then picked it up before walking out of the London Street store with two friends.

Following the incident, at about 10pm on Thursday night, staff alerted police who tracked the man to the top deck of a bus on Theatre Street, where he was arrested by firearms officers around half an hour later, in dramatic scenes in front of onlookers.

Witnesses to the row in Tesco said the gun was a black pistol and that staff had been "terrified" by the ordeal.

The man was tracked to the Number 21 First Bus, which goes to Bowthorpe, after the driver called the police when he refused to pay and would not get off the bus.

Firearms officers stormed the vehicle and found the man at the back of the top deck. 

A photograph taken by a member of the public shows officers pointing a gun at him.

Eastern Daily Press: Armed police were seen pointing a gun at a man upstairs on a Norwich busArmed police were seen pointing a gun at a man upstairs on a Norwich bus (Image: Submitted)Eastern Daily Press: Tesco in London Street, NorwichTesco in London Street, Norwich (Image: Submitted)

Police arrested three people on suspicion of being in possession of a firearm - a man in his 20s, an 18-year-old and another teenager - and seized a weapon, which they said was a BB gun.

READ MORE: Police point gun at armed teen on bus in Norwich city centre

They have been taken to Wymondham Police Investigation Centre for questioning where they remain.

One eyewitness of the arrest said: "I was absolutely shocked to see it, I felt so sorry for the poor bus driver and all the passengers.

"When the police arrested the man and took him off the bus he seemed to be laughing and joking."

Eastern Daily Press: Police at the scene in Theatre Street, NorwichPolice at the scene in Theatre Street, Norwich (Image: Submitted)