A suspected armed robber who tried to hold up a London bank with an AK47-style assault rifle and then caused panic when he fled through a pub, has been arrested after being apprehended by members of the public.

The suspect threatened staff at a branch of Barclays Bank in Borough High Street with a firearm and demanded they hand over money. But he fled empty handed with people believed to be bank security in pursuit, running through a nearby pub in an attempt to escape.

Customers reportedly dived for cover as the gun-wielding man, said to be in his 30s, was chased through the George pub, which was packed with lunchtime drinkers.

The suspect was shortly apprehended by members of the public, who detained him until officers from the Metropolitan police's flying squad arrived and arrested him.

Darren Burn, an ITV News journalist who was in the pub at the time of the incident, said: "I was having a quiet drink with my uncle and a friend when we heard tyres screech then saw a man with a gun.

"Bank security were shouting – they were telling us the man had a gun and we needed to get down.

"There were about 40 people in the pub courtyard at the time. It wasn't terrifying at the time, it all seemed a bit surreal.

"There were no screams, everyone just fell silent because it was a bizarre situation."

Burn, who lives in London, said the firearm looked like an AK47, although police were unable to confirm the type of weapon used.

He said: "I saw the suspect, he was making eye contact with people – but he looked pretty vacant."

A Metropolitan police spokesman, who described members of the public who detained the man as "brave", said officers were called at 1.47pm.

He said: "The suspect entered the bank and threatened the staff with a firearm and demanded that money was handed over.

"Desperate to escape, the suspect fled the bank empty-handed but was apprehended a short while later by members of the public.

"Officers arrived at the scene and the man was arrested. He was taken to a south London police station where he remains.

"No shots were fired and no members of the public were injured during the incident."

A weapon has been recovered, police said.

The incident is being investigated by detectives from the Tower Bridge flying squad.