Police seized properties worth at least $7.3 million and four luxury European cars after raids across Auckland on Wednesday.

After simultaneous dawn raids targeting what police called a major money-laundering operation, six people including a 65-year-old woman were arrested.

And multiple domestic bank accounts holding about $727,000 have been frozen after search warrants were executed in Remuera, East Tamaki Heights, Papatoetoe, and Karaka.

Detective Senior Sergeant Wayne Gray, of the Financial Crime Group, told Stuff one pistol and one rifle was also seized, and agencies including NZ Customs and the Department of Internal Affairs were also involved in the operation.

He said several different alleged "crime types" were involved and some of it came from alleged drug offending.

"This group is basically a group that facilitates organised crime," Gray added.

The group allegedly aimed to give the appearance of dirty money being legitimate, he added.

A $280,000 Bentley Bentayga​, a Mercedes GLS worth $120,000, Porsche Cayenne and a Mercedes C Class were seized.

Six people faced various charges including money laundering and unlawful possession of firearms and ammunition.

All the arrested people had been in New Zealand for several years but they had a variety of different citizenship or residency statuses, Gray said.

Police also found $250,000 in cash in one location alone.

The seized assets were now with the office of the Official Assignee.

The total value of seized assets was about $9million, Gray said.

Three men and three women were arrested and police said more arrests were possible.

Some of those arrested appeared in Auckland District Court on Wednesday afternoon and others were expected to appear on Thursday.

A 65-year-old woman faced six money laundering charges and a charge of "structuring" under the Anti-Money Laundering and Countering Financing of Terrorism Act.

A 41-year-old woman facing money laundering charges appeared and was granted bail. 

A woman aged 33 faced one money laundering charge. She was granted bail and ordered to reappear on September 18. 

She appeared in front of Community Magistrate Jan Holmes who granted her interim name suppression on "fairly slim grounds".

A man aged 36 was also remanded on bail to appear in court in September and granted interim name suppression. 

A man aged 38 faced 22 charges, including 20 of money laundering.

A 35-year-old man faced three money laundering charges, two charges relating to Class A and Class B import attempts, and three charges relating to unlawful firearms and ammunition possession.

Defendants who appeared in court were all ordered to surrender their passports and banned from entering ANZ banks or any other financial institutions to deposit cash or cheques.