An alleged armed robber has plunged to his death from a building’s fifth floor balcony while fleeing police in inner Sydney.

The man came to the attention of police after he allegedly threatened a staff member with a large knife at a convenience store on Devonshire St in Surry Hills about 8.05pm on Sunday.

CCTV obtained by 7NEWS shows the masked 49-year-old offender storming into the store with the weapon, and a customer trying to fight him off with a mop.

Know the news with the 7NEWS app: Download today

The robber stole the cash register and fled with a woman waiting outside.

No one was injured.

Following inquiries, police allege they tracked the man to a unit block on Belvoir St about 9.10pm.

When officers arrived, he and a 21-year-old woman, Tiahna Hatch, were waiting in the hallway.

The man spotted police and fled towards the back of the building, leapt from a balcony and fell five storeys.

Police provided first aid before paramedics took him to St Vincent’s Hospital, where he later died.

He is yet to be formally identified.

Hatch was arrested after allegedly shutting the door on police.

She has been charged with robbery while armed with a dangerous weapon, damaging property, and hindering police.

She was refused bail and was scheduled to face Bail Division Local Court on Monday.

Acting Assistant Commissioner Scott Tanner said the man and Hatch were known to police.

A crime scene has been declared, and a critical incident team from Inner West Police Area Command will investigate the circumstances.