Staff and customers stopped frozen as a brazen robber barged into a takeaways shop brandishing a large knife and demanded money.

The incident unfolded about 4.30pm at the May Wah Takeaways in Mangere East, South Auckland after the offender walked in through an unlocked back door.

Shop worker Linda Zhong said she and about four other staff members were busy taking orders for several customers when the man came in.

"He held the knife up and said 'Just give me your money'," Zhong said. "I just froze."

The man went to the front of the shop where the till was and emptied several hundred dollars from it before fleeing out the back entrance.

Zhong said the robbery happened quickly but she noticed the man was wearing a red chequered shirt.

"He was big."

She said his face was not obscured and she described him as possibly being Polynesian.

The back door exited into a carpark where shop workers parked.

Zhong said she noticed the man hanging around for a while outside, trying to "blend in" before he came inside.

"We're lucky no one was hurt."

There had been one other aggravated robbery at the shop in the six years Zhong had worked there, and that was last year.

Police said they were investigating the incident and were last night at the takeaways shop taking statements from the owner.