Another man, Bekim Muhtari, 29, of Hillside, has become the fifth person charged with murder over the death.

Mr Muhtari appeared in an out of sessions court hearing on Tuesday and was remanded to appear in the Melbourne Magistrates Court on Wednesday.

It is alleged that Mr Sleiman, 20, was ambushed in a Deer Park home by up to 15 men who were wielding baseball bats, poles and machetes on January 26.

Mr Sleiman, from Diggers Rest, had been drinking with his girlfriend, who was also badly injured in the attack, and about five other friends when the Millbank Drive house was stormed. Windows were broken and a ute parked outside the home was also badly damaged. Witnesses to the ambush said the attackers were wearing balaclavas or dark, hooded jumpers.

It has emerged that several of those linked to the murder were involved in a shadowy support club for the Rebels, known as Independent, that mostly operates in Melbourne's west. The club held a car show at the Rebels Sunshine clubhouse last year, and several patched Rebels were members of Independent before nominating.

After his death, friends of Mr Sleiman said he had been caught up in the wrong crowd. Last month, his large family marked what would have been Mr Sleiman's 21st birthday.

Thirteen people were taken into custody on Tuesday, five of whom were questioned over Mr Sleiman's death, which police believe involved a dispute between two groups that was not motivated by bikie activity.

"It wasn't bikie on bikie," Assistant Commissioner Stephen Fontana said. "This was an act of a group of bikies that targeted another person that wasn't associated with outlaw motorcycle gangs.

"We're not going to stand back and tolerate this intimidation, threats and violent activity by these types of criminal organisations."

Those being questioned over the death included a 21-year-old St Albans man, a 17-year-old from Caroline Springs, a 27-year-old from Albanvale, a 24-year-old from Cairnlea and a 20-year-old Deer Park man.

Deer Park man Benjamin Borg, 19, Adam Power and Jamie Fisher, both 23 and from Caroline Springs, last week appeared in the Melbourne Magistrates Court, each charged with one count of murder over Mr Sleiman’s death.

Matthew Delamothe, 22, of Deer Park, has also been charged with murder.  All four are due to appear in court again in November.

Eight other bikie associates or members arrested on Tuesday were expected to be charged in relation to drugs and firearms offences, parole breaches and theft of a motor car.

More than 300 police were involved in raids on 20 properties linked to the Rebels that led to seizures of drugs, weapons and vehicles.

Police who forced entry at one property faced "some resistance" from a man they were seeking to question over the death.

A 46-year-old Mount Cottrell man was remanded for breaching parole, a 50-year-old man was bailed for failing to appear in court, a 20-year-old was released and is expected to be charged with possessing a drug of dependence.

A 22-year-old man was charged with criminal damage and attempted theft from a motor vehicle, a 24-year-old was cautioned over drugs, and a 39-year-old woman was released without charge.

Two other men, both from Mount Cottrell, aged 54 and 51, were also being held in custody.

Detectives from the homicide squad, anti-bikie Echo taskforce, the AFP, Customs and the national Attero taskforce, which is aimed at disrupting the Rebels, were involved in the dawn raids.

Police executed warrants at seven Rebels clubhouses at Sunshine, Dandenong South, North Geelong, Kilsyth, Sunbury, Travencore and Pakenham and private properties linked to Rebels members.

The operation was also targeting weapons and drugs and comes after similar moves on the Rebels in Tasmania and Queensland in recent days.

The Australian Crime Commission said the raids also uncovered evidence that four Rebels with links to Tasmania and Queensland had imported more than eight kilograms of amphetamines from Britain worth $20 million in Australia.

The heavily fortified Sunshine clubhouse was blocked off by a line of police officers on Tuesday morning. Police removed objects concealed within large brown bags from the premises.

"It’s also looking at other criminal activity that this particular outlaw motorcycle gang might be involved in," Mr Fontana said.

"At this stage we've seized some drugs, firearms and a vehicle that we believe is stolen and we're still in the process of interviewing a number of people.”

Police say they seized drugs, including a quantity of white powder that had not yet been tested, steroids, ammunition, a gun, other weapons and vehicles, including a caravan and a motorbike, during the raids.

Over the past year, Victoria Police has charged 288 members of outlaw motorcycle gangs with more than 1293 criminal offences, Mr Fontana said.