Several injured as up to 100 bullets fired in shooting

A man has been arrested after an active shooting in a busy Sydney suburb that saw at least one person shot, numerous people injured and multiple cars fired upon by a gunman.

As many as 100 shots rang out over a two hour window between 7.45pm and 9.30pm on Sunday night in Croydon Park, in Sydney's inner west.

Streets were closed and the area was placed in lockdown as police launched a major operation after reports a man was indiscriminately firing at innocent motorists, including police cars, travelling along Georges River Road.

Described as an 'active shooting situation' by NSW police, Tactical Police Unit were called in to arrest a 60-year-old man from a unit above a business along the busy road.

Acting Superintendent Stephen Parry told reporters it is unclear exactly how many shots were fired "but there could have been anywhere between 50 and 100 shots that have been discharged".

He said numerous vehicles and premises sustained gunshots and damage during the incident, but a clearer picture would be available in daylight.

Supt Parry said the scene was secured 'fairly quickly' and praised the officers involved.

"They exhibited extreme levels of bravery in doing what they did," he told reporters in a late night press conference.

"They were under rapid fire gun shots on a number of occasions and should all be commended for their actions."

He was unable to confirm whether officers also fired their weapons during the stand-off.

Paramedics treated 16 people at the scene for minor injuries, some who were injured by shattered glass as their windows were hit by the bullets and others were treated for shock.

Two people were taken to hospital after being treated by paramedics.

A man in his 50s appeared at Canterbury Hospital with wounds to his neck and head.

He was later transported to Royal Prince Alfred Hospital in a serious condition.

The 60-year-old man is under police custody in Bankstown Hospital and is expected to be questioned and formally charged on Monday.

Firearms, including a high calibre rifle, were also seized during his arrest, police said.