Shoppers and staff at a busy Auckland shopping mall watched in horror as two men armed with hammers robbed a jewellery store, smashing their way into display cases.

The smash and grab robbery at Michael Hill Jewellers at NorthWest Shopping Centre happened at 9.40am today.

The thieves smashed glass display counters and stole an unknown amount of jewellery before fleeing the mall.

Police at the scene of smash and grab. Photos / Hayden Woodward

One witness said there was no sign of security guards when the men rushed into the store and "smashed, grabbed and dashed".

"It was fast, it seems they had a getaway vehicle waiting for them.

"I reckon they got away with a fair bit of stuff from the scene."

Allure Beauty Salon worker Baljeet Kaur said she saw two men whose faces were covered run in armed with hammers.

"They were big guys," she said.

"It was very scary, they ran in and smashed the boxes, it's where the expensive stuff goes.

"My heart is still beating fast, it's scary, and the first time in my life I've seen this."

A police spokesman said police are at the scene and making follow-up inquiries to identify and locate the offenders.