Woolworths is rolling out body cameras at all its 191 stores this week, as part of staff safety measures.

The supermarket chain trialled the cameras in 17 stores and says staff felt safer and reported the cameras helped de-escalate conflict and abuse from customers.

Woolworths has seen a 75 per cent increase in physical assaults and 148 percent increase in "serious reportable events" in the past three years.

The cameras are worn round the neck and only turned on during a security incident, Woolworths New Zealand director of stores Jason Stockill says in a statement. Staff are required to notify customers before recording.

"Footage will not be released except when requested by police as part of an investigation."

Woolworths NZ's head of health safety and wellbeing Denva Wren says there has also been a rise in the number of verbal threats.

"These range from threats to injure, threats to come back after the store is closed, threats to kill. It's really awful and unaccaptable."

The rollout is part of Woolworths' three year, $45 million programme to add more security measures to stores.

Other measures include walkie talkies and trolley lock systems.

"Every security measure implemented in Woolworths stores complies with New Zealand law including privacy requirements," Stockhill says.

-RNZ.