"In a combined operation, police and prosecutors raided more than 30 premises and arrested 20 people," in the southern Limburg and Brabant provinces, as well as in Belgium and Germany, the police said in a statement as the operation continued.
"The raids are based on a long-running investigation into criminal activities. Most of those arrested are members of the Bandidos outlaw motorcycle gang," the statement added.
Police chief Gery Veldhuis later told a press conference that five rocket launchers were found in the raids, along with several automatic rifles and handguns and a synthetic drug laboratory.
The suspects faced charges of assault, violence, extortion and money laundering, he said.
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Today's raids follow concerns about rising tensions over turf between so-called "one-percenter" or outlaw motorcycle gangs.
The Bandidos last year opened its first local club, or chaptr, in the Netherlands in the southern town of Sittard.
Observers say the move raised the hackles of the rival Hells Angels.
The province has since seen a rise in violent incidents, including hand grenades thrown at the homes of gang members and fights between rival outfits.
Some biker gangs have been linked to organised crime, including drug running, prostitution and weapons trafficking.
Earlier this month, nine people died and nearly 200 were arrested in the US state of Texas after a gunfight between the Bandidos and the Cossacks, a local biker group.