Police say a 12‑year‑old boy has been arrested after allegedly walking through Adelaide’s Rundle Mall with a 53cm stainless‑steel machete concealed down his pants — all while being watched live on the city’s CCTV network.

Officers monitoring the cameras allegedly saw the boy and moved in. When they approached, police say the child — from Tea Tree Gully — tried to run.

WATCH ABOVE: Teenager caught with massive machete in Adelaide CBD

Know the news with the 7NEWS app: Download today

He was arrested a short time later on Grenfell Street.

Police say they found the machete hidden in his clothing, along with a balaclava described as an “article of disguise”.

7NEWS has obtained security vision of the afternoon foot chase.

CCTV captured the teen in the mall. Credit: 7NEWS

Officers initially arrested the 12‑year‑old and a 15‑year‑old, before a third boy allegedly tried to open the patrol car door to let them out.

All three were bailed to appear in the Youth Court at a later date.

The machete. Credit: SAPOL