Police in Perth believe they have smashed an organised crime syndicate following the seizure of four kilograms of methylamphetamine.

They said the seizure of two kilograms of drugs during a routine traffic stop in January led to a four-month operation which culminated in raids on six properties in Perth in April.

Police seized methylamphetamine with a street value of $8 million, firearms and $380,000 in cash.

Two of those charged are Ziad and Rabih Jneid.

Police said some of those arrested during the raids were part of a sophisticated drug ring.

"They're at the top of the hierarchy as heads of a syndicate, so these are significant players," Detective Inspector Chris Adams said.

"When you are caught in possession of up to four kilos you are a significant importer of methylamphetamine."

Police media's Sam Dinnison said some drugs were initially found when police stopped a car in Kewdale in January.

"Officers located and seized approximately two kilograms of methylamphetamine after searching a vehicle they had stopped," he said.

"The driver initially failed to stop and attempted to evade them."

Mr Dinnison said in the following weeks, a further two kilograms were seized by Organised Crime Squad detectives.

"It will be alleged the drugs were from the same drug syndicate," he said.

In April, 70 police raided six properties in Kewdale and Bibra Lake.

"It will be alleged a search of those properties resulted in the seizure of over $380,000 cash, two firearms, ammunition, steroids and pepper spray canisters," Mr Dinnison said.

Two men from Kewdale, a 38-year-old and a 40-year-old, were charged with a number of drug offences, including conspiracy to sell or supply a prohibited drug.

A 40-year-old man from Bibra Lake was also charged with the same offences.

A 33-year-old man from Munster was charged with supplying a prohibited drug and possessing a firearm without a licence.

Those charged will face court in July and August.

Two other people have been charged by summons in relation to firearms and weapons offences.