Four men are dead, a woman has been wounded and the alleged gunman responsible is under police guard in hospital after a bloody rampage in five different locations throughout Darwin.

The 45-year-old suspected gunman, who was on parole, was arrested after being on the run for about an hour following the mass shooting in and around a hotel in Darwin's CBD on Tuesday.

On Wednesday morning, Northern Territory Police Commissioner Reece Kershaw said the offender had used a prohibited firearm, that may have been stolen as far back as 1997.

Northern Territory Chief Minister Michael Gunner said an "active police investigation" is continuing on Wednesday across eight active crime scenes.

The first victim has been identified as Lebanese-born Hassan Baydoun, who worked in Darwin as a taxi driver.

AAP

"We've asked for a detailed report from the Parole Board of the alleged offender and directed an immediate review of the 103 people currently on parole," Mr Gunner said.

"It will be completed by the end of next week. While we have no reason to believe an event like this will occur again, it is critical we make every effort that it does not."

Speaking to reporters, Commissioner Kershaw said there were early indications that the gunman was looking for a specific person called 'Alex' who is currently located outside of the Northern Territory.

It is currently unclear if the four victims were known to the attacker.

Police have also called for information about three cars - a White Toyota Hilux, Red Commodore and Silver Proton - which they believe were involved in the incident.

Television footage showed the suspected gunman on the ground being dragged from under his white dual cab ute, kicking his legs at officers from NT Police's Territory Response Group.

The incident started with reports of a man firing shots at Finnis St at about 5.50pm just outside the Darwin CBD, with the four deaths occurring at the nearby Buffalo Club, Gardens Hill Crescent, the Palms Motel and Jolly St.

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The suspected gunman also tried to enter the Peter McCauley Centre police station to possibly hand himself in, then phoned a duty superintendent who did a "magnificent job in negotiating with him" before the arrest, Police Commissioner Reece Kershaw told reporters.

At least 4 dead in Darwin CBD shooting, multiple crime scenes across the city with one man arrested here. We are hearing he entered a motel with a pump action shotgun @abcnews @abcdarwin pic.twitter.com/6SMnyCusuy — Stephanie Zillman (@Steph_Zillman) June 4, 2019

The alleged shooter is an outlaw motorcycle gang member, well known to police with a criminal history, and the incident is not believed to be terror-related.

Mr Kershaw said the suspect was released from prison on parole in January after serving at least a year, was wearing an electronic monitoring bracelet, and had acted alone on Tuesday.

ABC NEWS

"He is an individual who is well known to police and has a number of interactions, adverse, with the police force," he said.

"We're still trying to establish the intent and the motivation behind this but all I can say is that, sadly, people have lost their lives this evening."

The man is being held in custody in the hospital as a precaution.

Reports an active shooter in Darwin CBD with up to 20 shots fired and people injured ... confusing scenes with tree on fire and roads blocked. pic.twitter.com/4WY2hVE2b3 — Stephanie Zillman (@Steph_Zillman) June 4, 2019

A group of about a dozen men who were friends and relatives of the man who died at the Palms Hotel gathered outside, many in tears.

Local Matthew James helped patch up a woman who had been shot in the leg near the Palms.

She is in hospital in a stable condition, an NT Health spokeswoman said.

"She was caught up in it, she said 'I've been shot, I don't know why I don't have anything to do with anything.' She was hysterical obviously," Mr James told AAP.

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The woman who had been shot told Mr James the shooter had been going from room to room, shouting the name of a man he wanted to see and firing his gun.

Chris Dalgleish, who was having a beer on the balcony of the Frontier Hotel pub across the road from the Palms, said people heard shots and raced inside the pub when they realised it was a gun.

AAP

"Everyone started jumping inside, then locking doors and windows and went to the back corner," he told AAP.

Facebook user John Rose said he witnessed a man "shoot up the Palms Hotel".

"He was wearing high-vis, we found one person in the rooms that he shot up. Scary," Mr Rose posted.

"We watched him like 20 feet away, calmly walk into the hotel room shoot the door open and then proceeded to shoot up every room," he wrote.

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Speaking in London, Prime Minister Scott Morrison said the shooting was a "terrible act of violence".

"I just want to extend my deep condolences and sympathies to all the people in the Territory and particularly in Darwin," Mr Morrison said.

"This is a very tight community and I know they will be rocked by these events."NT Chief Minister Michael Gunner said it was a devastating day for the Territory, "this was not the Darwin we know", and his thoughts were with the families and friends of the victims.

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