Police are negotiating with a man dangling off the roof of an apartment block after the shocking discovery of a woman's body on Sydney's north shore.

A pedestrian made the grisly discovery of the woman's body in an alleyway at about 6.30am (local time) on Brown Street near Chatswood train station.

The woman appears to have fallen from somewhere in the Brown Street apartment building.

Police and a Korean interpreter are now speaking to the man who is dangling above an awning over a communal gym area of the building and occasionally stretching his arms out over the ledge.

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The man has now taken off his shoes and placed them on the awning, and can be seen occasionally glancing anxiously back over his shoulder into the gym behind him, where a crime scene has been established.

It is believed the discovery of the woman's body is linked to the police incident currently at the scene, where a large crowd has gathered to watch.

One woman told news.com.au police had stopped her leaving the building.

She said her young children were alarmed to hear about the death of the young woman.

After the passer-by contacted emergency services early on Monday morning (local time), police and paramedics arrived on the scene.

The dead woman was thought to be aged in her 20s.

A NSW police spokeswoman said no other details, including the cause of death, were yet available.

The area is close to a number of apartment buildings and several businesses.

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More to come.

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