A teenager shot dead in a convenience store was an innocent bystander caught up in a suspected gang fight, Scotland Yard said.

The victim, thought to be 18, was killed at a Costcutter shop in Walworth, south east London, on Wednesday evening.

Police said he was shot moments after two other black men of a similar age pushed their way into the shop behind him. As the pair, who were believed to be trying to get away from someone, forced their way inside several shots were fired.

One witness said the victim was hit in the back of the neck as panicked shoppers attempted to escape.

Officers are hunting up to five male suspects who drove away on three mopeds in the direction of Boyson Road. Those responsible may have been prowling the area for some time, possibly as they looked for their intended victims, police said.

Investigators were also probing whether the murder is linked to a shooting in Lambeth earlier in the day when a youth was hit in the leg.

Det Supt Gary Richardson, of Operation Trident, said his officers are keeping an open mind as to the motive. He said: "It appears at this stage that the victim has no links to gang activity and that he was an innocent bystander - caught up in the cross fire and was not the intended target."

The victim was the 22nd teenager to be killed violently in the capital this year.

Police were called at about 9.40pm to the Walworth Road store, which is close to the junction with Camberwell Road. Police and paramedics attempted to save his life but he was pronounced dead at the scene at 10.25pm.

A 19-year-old man has been arrested on suspicion of murder and is being held at a south London police station.