Police have impounded several bikes, seized vehicle plates and issued around 100 infringement notices in a road policing operation to monitor a gang event taking place in Auckland.

Revving engines filled the air and curious residents emerged from homes to watch as dozens of Head Hunters set off on a cross-city motorcycle run to mark the 20th anniversary of the gang's most influential chapter.

Around a dozen police officers in eight patrol cars set up checkpoints east and west of the East chapter's Marua Rd, Mt Wellington pad, and on the adjacent Burt/Rutland roads intersection as around 50 patched gang members left on motorcycles about 11am.

"This has been very effective and we have stopped and checked every motorcycle in the convoy," said Inspector Regan James.

"We are continuing to monitor group bike rides and offending on the roads will be investigated and followed up with enforcement action."

Several bikes have been impounded for a variety of offences, including driving while disqualified and driving while suspended, vehicle plates have been seized and around 100 infringement notices are to be issued.

Earlier, police in an unmarked car could be seen taking photos of gang members gathered outside the pad.

The Eagle police helicopter also circled above but the gang members weren't stopped as they headed east on Marua Rd en masse bound for, according to sources, the north Auckland settlement of Puhoi.

The motorcycle run is part of celebrations this weekend, understood to involve hundreds of Head Hunters, marking the chapter's 20th anniversary.

Head Hunters at the Marua Rd property. Photo / NZME

Police were aware of the gathering, a police spokeswoman said before the motorcycle run began.

"There will be an increased police presence in the area, for community reassurance and to respond to any issues if they arise.

"Any unsafe, intimidating, or dangerous behaviour occurring throughout the event/s will be followed up by Police and appropriate action taken."

Concerning behaviour could be reported to police by calling 105.

After the gang members left for their journey to Puhoi, police checkpoints remained in place, with one stopping motorists to check driver licences.

The East chapter was established by the gang's president, Wayne Doyle, in 2002 when he completed his prison sentence for the murder of a rival gang member in a brawl.

The Head Hunters had a chapter based in West Auckland but on his release from prison, the gang expanded into the eastern suburbs by buying sprawling premises in Marua Rd in Mt Wellington.

Initially a tight-knit group of around 30, the Head Hunters have now grown to have an estimated 500 patched members and prospects across the country.

A number of senior members have been convicted of serious methamphetamine dealing over the past two decades, and have a reputation for intimidation and violence in the criminal underworld.

The Herald understands police are closely monitoring the Head Hunter event as part of Operation Cobalt, which includes a dedicated taskforce of staff in Auckland, to "suppress, disrupt and enforce" unlawful gang activity.

While the police have successfully targeted gangs in covert investigations into drugs and organised crime over many years, in recent weeks police have used more overt tactics to keep an eye on gang behaviour.

Police followed the Comancheros "gang run" from Auckland to Waikato, issuing Infringement tickets at a petrol station, and a week later set up a checkpoint to stop a convoy of Killer Beez.

Any large gathering of Head Hunters riding in unison this weekend will almost certainly be targeted by Operation Cobalt.

The Head Hunters gang are gathering to celebrate the 20th anniversary of the influential East chapter. Photo / Brett Phibbs

The show of strength to mark the 20th anniversary of the East chapter comes as the Head Hunters have been challenged by new contenders in the gang world and police pressure on Doyle.

Last month, the Marua Rd pad was attacked in a late-night drive-by shooting.

The gunfire was believed to be in retaliation for a member of the rival Mongols gang being shot in an Auckland strip club a few days earlier.

It was the third such brazen attack on the Head Hunters pad in recent years; each linked to new Australian gangs, the Comancheros and the Mongols, which have upset the pecking order in New Zealand.

Nicknamed "501s" after the section of the immigration law used to deport them from Australia on character grounds, police believe these gangs have a disproportionate influence on the criminal underworld because of their international connections, sophisticated counter-surveillance tactics, and aggressive approach to using firearms.

While New Zealand criminals have always carried firearms, the arrival of so many rival groups has escalated tensions to the point where someone is more likely to pull the trigger.

One tit-for-tat feud with the Mongols, for example, led a member of the Head Hunters to open fire in the lobby of a five-star hotel on Auckland's waterfront.

At a wider level, data recorded by frontline police show staff are coming across about 10 firearms every day.

"There doesn't seem to be many days go by when you don't hear about shots being fired," Police Association Chris Cahill said earlier this week.

"That flows from the fact there is a willingness to actually pull the trigger. It demonstrates why we have to do everything we can to put this genie back in the bottle."

Police talk to senior Head Hunters gang member Wayne Doyle during the termination of Operation Coin in 2017. Photo / NZME

As well as facing down threats from rival gangs, the leadership of the Head Hunters has been targeted by police in recent years.

Several senior members received lengthy prison sentences for methamphetamine offences, including William "Bird" Hines, who is also battling ill health, and David O'Carroll.

On the back of those investigations, the police have restrained about $10 million worth of property linked to Wayne Doyle, who has not been convicted of any crimes since his release from prison 20 years ago.

Five properties across Auckland, including the gang's Marua Rd headquarters, have been frozen since September 2017 when the High Court granted restraining orders after a police investigation, Operation Coin, into his financial affairs.

Although not alleged to be personally responsible for the criminal activity of other Head Hunters, the thrust of the police case is that Doyle received significant financial benefits because of his status as the alleged leader of the gang.

These alleged payments allowed him to accrue the restrained properties, now valued at more than $10m, despite having declared no income for many years, according to the police.

The court case has already dragged on for nearly five years. The trial has been postponed twice, but a judge-alone hearing has been scheduled for October next year.