Terrifying video captures 'machete-wielding' woman allegedly robbing a Sydney supermarket.

A woman has been arrested after she allegedly brandished a machete in an attempt to rob a supermarket in Sydney’s north.

The 31-year-old strolled into the Neutral Bay Woolworths about 6.30pm on Tuesday, where she allegedly confronted staff, stole items from the service counter and pulled out the weapon to threaten a male staff member.

A customer, identified only as Nick, told Channel 9 he witnessed the woman, who had a black scarf covering the lower half of her face, ordering checkout staff to hand over cash.

“She was going from till to till to till, until she worked out she actually couldn’t get any of them open,” he said.

“I guess that’s when it became very serious, because… she actually cornered one of the young attendants in one of the actual checkout aisles.”

Nick approached the woman who he says then chased him out the door of the supermarket, and fled toward busy Military Rd.

He and another bystander, named Victor, gave chase and managed to restrain her until police arrived.

“I grabbed her from behind in a big bear hug and kind of lifted her off the ground as much as I could,” Nick told Channel 9.

“He [Victor] ran in from the right-hand side, grabbed both of her hands. He must have put pressure on her wrist or something like that, got the machete off her and threw it away.

“Then I’ve literally lifted her off the ground and placed her on the ground gently – not really. And then we just kind of held her until the cops came. By that time we could already hear sirens.”

Nick heroically tackled the woman responsible. Image: Channel 9.

The woman was arrested and taken to North Sydney Police Station where she was charged with larceny, being armed with intent to rob using an offensive weapon, wielding a knife in public place, common assault and being armed with intent to commit an indictable offence, reports Channel 9.

She was refused bail and is set to appear in Central Local Court later today.