More than 180 foreign nationals are being questioned by authorities after police raided properties across Perth as part of an operation against organised crime.

An area of Carabooda in Perth's northern suburbs was shut down after Tactical Response Group officers smashed through the gates of a walled community containing about six houses early Saturday morning.

Firearms, cash and computers were also seized in the raids, part of operations dubbed Project Tricord and Operation Polo, targeting money laundering and other crimes.

Customs officers on Saturday morning also questioned people at neighbouring properties, which included a tomato farm surrounded by high barbed wire fences.

Women and children are understood to be among the dozens questioned but police say the main focus of the raids is not on them, but on a money laundering operation.

Acting Superintendent Chris Adams said 550 law enforcement officers, from agencies including the Australian Federal Police, Department of Immigration, Customs, the Australian Securities and Investment Commission and the Australian Tax Office, were involved in the operations.

Police gather in Carabooda as part of an investigation into crime syndicates. ( Western Australia Police )

"This is certainly the biggest investigation, from a joint approach, from an organised crime perspective, that certainly the WA Police have been involved in, in WA," he said.

"Nothing of this scale has ever happened before ... it has significantly dented crime in the state."

He says it is believed the crime syndicate has been operating for about 10 years.

Acting Superintendent Adams says the police operation has been ongoing for 12 months in the lead-up to the sting, which spanned Western Australia and Victoria.

On Saturday morning, a bus carrying passengers and escorted by a police car passed a road block on Bailey Road in Carabooda.

Police have issued a statement advising members of the public not to be concerned by the police presence.

Police raided other properties across Perth on Friday evening in a crackdown on crime syndicates.