Two associates of the Comanchero outlaw motorcycle gang have been charged as part of an investigation into alleged extortion and a firebombing that targeted a Perth business.
In May, the state commander of the Comancheros, other bikie members and associates were charged over their involvement in the alleged incidents.
On Wednesday, officers arrested two more men, aged 35 and 24.
They have each been charged with demanding property by oral threats and an unlawful act with intent to harm.
Both are due to appear in Perth Magistrates Court on Thursday.
Police said there had so far been 10 people charged over the incidents.