Three armed robbers were arrested after a gang of twelve robbed three stores at a Boksburg shopping centre on Tuesday afternoon, police said.

The 12 men divided themselves into three groups which simultaneously robbed a bottle store, a butchery and a take-away shop at the Rosedene shopping centre at 4.30pm, said Captain Mack Mngomezulu.

They managed to steal about R40 000 from the three shops.

Shoppers who witnessed the robbery alerted the police, who quickly responded.

"Police arrested three of them, but nine managed to escape in a blue Kombi and white Toyota Corolla.

"Before storming into the shops, they robbed an off-duty traffic officer of his service pistol. He was also at the shopping centre," said Mngomezulu.

Those arrested were aged 23, 29 and 30.

Police seized four firearms, which had their serial numbers removed, and 30 live rounds of ammunition. The cash was not found.

"There are people who managed to get the Toyota Corolla's registration number. Police are looking for it and more arrests are expected soon," said Mngomezulu.