Abuzar Sultani did not come up from the cells on Wednesday morning as his case was mentioned in Newtown Local Court.

He was one of four men, all with links to the Rebels, arrested in co-ordinated raids across Sydney, on Tuesday.

Mr Sultani was apprehended in dramatic scenes in Sydney's Olympic Park as multiple investigations in which he was a target came to a head.

It is alleged Mr Sultani, who was previously a senior member of the Rebel's Burwood chapter, murdered Mr Barbaro, 35, in Earlwood, on November 14.

It is understood there were long-running tensions between the pair.

Mr Barbaro, who had links to the Calabrian Mafia, was shot dead while leaving the house of his friend and construction industry figure George Alex.

Fairfax Media understands Mr Sultani was also questioned about three other gangland killings: the shooting of Rebels figure Michael Davey in March, of Rebels Sydney City chapter sergeant-at-arms Mark Easter in 2015 and of Mehmet Yilmaz in September.

When Mr Sultani emerged as a suspect in the Barbaro shooting, he was already on the police radar for a number of other alleged operations.

Court papers detailed the raft of allegations against him, including that, over the past few months, he had 30 firearms in his possession and more than 9000 rounds of ammunition.

He is facing several charges over his alleged drug activity, which ranged from supplying ice at Hornsby in October to MDMA in Warwick Farm this month.

Police allege he also supplied two kilograms of methamphetamine in Olympic Park between August 10 and his arrest on Tuesday.

He became a target of the Gangs Squad's Strike Force Raptor investigation in November last year.

The investigation was looking into the activities of the Burwood chapter of the Rebels and was later joined by the Drug Squad.

Mr Sultani is also accused of conspiring to murder Ricky Ciano, a former Rebels enforcer who patched out of the club in recent years, on the Central Coast on August 18, 2015.

He allegedly had five guns in his possession on that day.

The 27-year-old did not apply for bail on Wednesday and the case was adjourned to Burwood Local Court on December 22.

Outside court, his lawyer John Hajje said his client "was doing all right".

Asked if he would defend the charged he replied: "We will wait and see what facts come in and we will have a look at the facts then."

The three other men arrested in Tuesday's raids were due to front court on Wednesday charged with the murder of Mr Barbaro.

The four were among nine men, aged between 18 and 29, charged following 13 raids on properties that senior police said was "phase one" in a crackdown on the city's underworld.

Officers also seized more than 40 phones, 11 cars, a safe, cash and stolen NSW Police identification. Police said they had already seized 43 firearms and 15 prohibited weapons including ballistic vests and silencers from their investigations into the group.

Tuesday's arrests follow the formation of Strike Force Osprey in the days after Mr Barbaro was shot dead.

The strike force was established to examine Mr Barbaro's death and seven other unsolved underworld killings in Sydney in the past 18 months.

Acting Deputy Commissioner Frank Mennilli said Tuesday's raids were carried out at Sydney Olympic Park, Wentworth Point, Baulkham Hills, Gladesville, Merrylands, Constitution Hill, Meadowbank, Five Dock, Alexandria, Silverwater and North Rocks.

He said he expected the nine arrests to be the first of many.

"There is no end game," he said. "We will continue to target these individuals through methodical investigations and disruption strategies. There will be ongoing arrests. We will be protecting the state of NSW.

"We will not be tolerating any individual who has a total disregard for the community of this state and its laws."

Fairfax Media has been told Mr Barbaro, a man with countless enemies in the criminal underworld, and Mr Sultani had a long tension-prone history.

While Mr Sultani was known to act as an alleged "heavyweight for hire", he had been suspected of carrying out his own violence for his own reasons in the past, police say.

He is believed to be the alleged ringleader in the killing of Mr Barbaro.

Mr Easter was last seen leaving his home in Little Bay in June 2015.

His bullet-ridden body was found dumped in bushland off the Pacific Highway at Cowan, north of Sydney, days later.

Police believed Mr Easter's death was an "inside job" orchestrated and carried out by someone within the bikie ranks.