A teenage boy accused of involvement in a Boxing Day row that sent shoppers running for their lives has admitted possessing a machete and been given bail.

The 16-year-old was arrested at the Intu shopping centre – formerly the Glades – in Bromley, south-east London, after a fight sparked rumours that a gunman was on the loose. Armed police attended the scene about 3.45pm on Saturday and found the boy with a head injury. Two knives were also discovered in the area.

The teenager, who cannot be identified for legal reasons, appeared at Bromley youth court on Monday and admitted possessing an offensive weapon, namely a machete, at Intu on Saturday. He also faces accusations of common assault and violent disorder but these have not yet been put to him.

District judge Dennis Lynch said he felt able to grant bail with stringent conditions: that the boy stays at a specific address and is indoors there from 7pm to 7am. He must only leave the address in the immediate presence of his grandmother, mother, father, aunt, or a youth offending team official. He was also ordered to keep out of Bromley town centre, except to return to the court on 5 January. His family had to deposit a cash security of £500.

Police said that a second boy, also 16, was arrested at his home in Lewisham, south-east London, on suspicion of affray.

Boxing Day shoppers told how they ran for their lives after a group of young people began to argue in a shoe shop. A video posted on Twitter showed shoppers screaming and running out of the centre.

Keith Moon, 35, an app developer, was out shopping with his wife when he saw people running in a chaotic scene. He later saw a boy in handcuffs, bleeding from the head, being led away by police, who were carrying a 60cm machete.

A Metropolitan police spokesman said: “Detectives are seeking to trace a number of youths who ran off from the scene shortly after the incident.”

Nelson Adeosun, 27, who works in television, said: “It was really busy because of the Boxing Day sales and there was a mass exodus of people on the ground floor. They were shouting and running. Adeosun, who was out shopping with his brother, said he feared for his life as he ran out of the building. He said: “People were running, some with children, and they were dropping stuff. It was a stampede.”