Six police officers and a man have suffered burns in a fire after a four-hour stand-off at a property in Sydney's south.

The fire occurred in the garage of a unit building on Stephen Road in Botany just before 3pm.

Police had been at the property since around 11.15am, after reports a 55-year-old man had barricaded himself inside the garage of the building.

A statement from NSW Police said "a fire erupted" when officers forced entry to the garage.

The fire occurred in a garage at the unit. (9NEWS)

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It is understood the man had doused himself in petrol and the fire was caused by him setting himself alight inside a car.

The officers were injured when they dragged him from the vehicle.

The man and three officers, including a 42-year-old who suffered serious injuries to the face, were taken to St George Hospital.

Two more officers, aged 35 and 50, were taken to the Prince of Wales Hospital with minor injuries, and a sixth was treated at the scene.

Emergency services at the Botany unit. (9NEWS)

The man remains under police guard in hospital with burns to his back.

Officers expect to formally interview him tomorrow.

Nearby residents on Stephen Road were evacuated during the stand-off.