A man has been fatally shot by police at a bustling shopping center in Sydney’s western suburbs.

Authorities responded to calls about a disturbance at Westfield mall in Mount Druitt around 3pm, a peak time filled with Saturday shoppers.

The altercation involved two groups wielding knives and machetes on the rooftop parking lot near the Hoyts cinema.

Police say one of them, a man aged in his 20s, was brandishing a machete when he turned on officers and walked towards them.

One or several officers fired shots and killed him.

Shoppers ducked for cover and hid in shops.

The man was treated by paramedics but died at the scene.

At least one woman was seen being taken away in handcuffs.

Police have launched a critical incident investigation.

Locals are being told to avoid the area.