New figures from police show the number of aggravated robberies on dairies and convenience stores has almost doubled in the space of a year.

There is now, on average, more than one robbery a day reported in South Auckland, with shop owners increasingly barring themselves behind metal bars as protection from offenders.

There were four 418 aggravated robberies in South Auckland alone in the past year. That's more than one a day.

Kamaljit Singh's Kingsford Supermarket in Mangere was one of those 418 after four men, two with machetes, entered his dairy and held an employee at the throat in May this year.

"They came from the back and hit him on the head and smashed him on the floor," Mr Singh said.

"They beat him up."

Charges of aggravated robbery have since been laid.

New figures from police reveal 1,237 such robberies have been reported at dairies and petrol stations in the past year - a figure that is 87 per cent higher than the year before.

Superintendent Eric Tibbott, who works as a crime prevention manager, says it's becoming a big concern for police.

"We've seen an increase in aggravated robberies which is really worrying for the police, worrying for the government and worrying for dairy owners," he said.

"But we're doing everything in our power to stem that flow."

Mr Singh says offenders are fearless - the 36 cameras in and around the store no deterrent to those who attacked his worker.

Now a fog machine's been added and all of his staff wear panic alarms.

An increasing number of dairies are also using metal bars to stay safe, with staff, cigarettes and cash on one side and customers on the other.