Abuzar "Abs" Sultani, a former head of the Rebels bikie gang Burwood chapter, is one of six men arrested over the murder of Mehmet Yilmaz, 29, who was shot multiple times as he returned to his car after visiting the home of a Comanchero bikie in September last year.

On a quiet suburban street in St Mary's, Mr Yilmaz's fiancee watched on as he was ambushed and shot at point blank range in the gutter outside the home of Hayan Chandab, a self-identified Comanchero gang member.

At the time, Detective Chief Inspector Grant Taylor of the NSW Homicide Squad said those responsible "certainly wanted to make sure this individual was deceased", highlighting the targeted nature of the execution-style killing.

The murder prompted the formation of Strike Force Estop, established by detectives from the State Crime Command's Homicide Squad and the Gangs Squad's Strike Force Raptor.

Their investigation also revealed Mr Yilmaz had been seriously assaulted and kidnapped in the weeks leading up to his death.

In the early hours of Thursday morning six search warrants were executed at properties in Meadowbank, St Marys, Blackett, Mt Druitt, Stanhope Gardens and The Ponds, conducted by investigators from Strike Forces Estop, Raptor, the Public Order and Riot Squad and the Dog Unit.

Homicide Squad Commander Detective Acting Superintendent Jason Dickinson said police would be alleging that Mr Yilmaz was ambushed in Brisbane Street and shot dead on September 9 last year.

"Following 12 months of an investigation ... we have been able to charge six men, who we will be alleging are all part of one criminal group with roles in Mr Yilmaz's death, and a further two men with their roles in the kidnapping and serious assault," he said.

"Our enquiries are continuing and we anticipate there will be further arrests in relation to these matters."

The arrests began last Thursday with 40-year-old Erkan Keskin, an alleged senior member of the Lone Wolf Bikie gang, who was charged with a number of offences, including kidnapping, occasioning actual bodily harm and knowingly giving misleading evidence to the NSW Crime Commission.

At the time of his arrest Keskin, a former Turkish soldier, was already on bail for drug charges in Queensland.

He appeared at Central Local Court on Thursday where he was granted bail under strict conditions.

Ergul Cakmakkaya, 46, was also arrested and charged in relation to Mr Yilmaz's kidnapping. He was refused bail to appear at Mt Druitt Local Court on Thursday.

A further six men were arrested in relation to Mr Yilmaz's murder, including 28-year-old Sultani, who was also charged with directing a criminal group. He will appear in Burwood Local Court on Thursday.

Sultani has already been charged over the execution style murder of Barbaro in 2016. The Mafia crime figure was shot dead as he left the Earlwood home on November 17, 2016.

A co-accused in the Barbaro murder, Joshua Baines, 25, has also been charged over the Yilmaz murder. Adam McNamara, 31, has also been charged with Yilmaz murder and participating in a criminal group.

Siar Munshizada, 28, and Aram Makinadjian, 28, were both charged with accessory after the fact to murder and participating in a criminal group.

Detective Acting Superintendent Dickinson said the arrests should serve as a reminder, that "just because we are not talking about investigations does not mean they are not continuing. We are still working on these matters".

He described organised crime murders as "notoriously difficult".

"They present significant challenges for our detectives," he said.

"We are dealing with people who are fearful, we are dealing with people who are uncooperative. These matters often involve a level of planning and they are calculated and that makes them challenging investigations."

While Mr Yilmaz's death was the focus of Strike Force Estop, it is one of eight gangland killings being explored by a separate body, Strike Force Osprey.

All eight victims involved in the killings had an organised crime association and in some cases the victims were known to each other.