Burglars have targeted seven Subway restaurants in eight days.

The cash hungry Subway burglars have struck again – forcing their way into two more restaurants in Christchurch.

The popular fast food chain was warned to beef up security after five of its stores in the city were targeted on separate nights last week.

Police revealed on Wednesday two more restaurants were hit within a matter of minutes late Monday.

All the burglaries appear to be the work of two men, who forced entry by jemmying open doors.

READ MORE: Rash of Subway burglaries in Christchurch

They targeted cash.

Detective Sergeant Craig Johnson said the spate of burglaries was "unusual".

"It's a concern to the businesses and it's a concern to us and we're certainly trying to bring this to an end."

Subway restaurants in the central city and Addington were broken into on Monday night, Johnson said.

Other stores in Parklands, Rangiora, Belfast, Mairehau and Linwood were targeted early on Tuesday and Wednesday morning last week.

Police believed a burglary at a Hell Pizza, which is next door to Subway on Harewood Rd, Bishopdale, was linked.

The burglars might have gone in the wrong door at the rear of the building.

Johnson said the same two people, wearing dark-coloured clothing, appeared to be responsible for the break-ins.

The pair usually forced entry through the front door using a tool, possibly a crowbar or a hammer.

They spent a matter of minutes inside before leaving in a station wagon.

Johnson said he was unable to say why the fast food chain was being targeted by the burglars.

"There's no indication that there's any grudge against Subway or any staff members," he said.

"It just seems [as though] they've found a system that works for them and they're sticking with it. Until we get bad people in hand there are going to be some unanswered questions."

Johnson said investigators were reviewing security footage of the burglaries and following some good leads.

Police had spoken to Subway and urged them to be vigilant about security and keeping money on site.

The fast food chain has more than 20 restaurants across the city.

Anyone with information should contact Christchurch police on 03 363 7400 or Crimestoppers anonymously on 0800 555 111.

FRESH EACH DAY: A RASH OF SUBWAY BURGLARIES

Tuesday last week:

- Thieves try to break into Subway Parklands, but are scared off when an alarm sounds at 12.41am.

- Thieves break into Subway Rangiora at 1.17am.

- Thieves break into Subway Belfast at 2.22am

Wednesday last week:

- Thieves break into Hell Pizza in Bishopdale 2.10am. Police believe the burglars might have been trying to get into the Subway next door but jemmied open thee wrong door.

- Thieves break into Subway on Hills Rd, Mairehau, about 3.40am. About that time they also break into Subway on Stanmore Rd, Linwood.

Monday:

- Thieves break into Subway South City at 11.35pm.

- Thieves break into Subway Addington at 11.42pm