Raided: Hells Angels.

Raided: Hells Angels. Photo: Kate Geraghty

Heavily armed police have raided a number of properties across Sydney as part of a co-ordinated hit on bikies and their gun and drug networks.

Shortly after 6am, hundreds of police raided at least four properties, in the CBD and Sydney's west, linked to the Hells Angels and Comanchero bikie gangs.

A number of people, believed to be senior members of those clubs, are in custody.

Police said raids were also carried out north and south of Sydney. Properties in Wollongong are believed to have been raided.

Police said the raids were part of a long-running investigation into the supply of firearms and drugs to organised crime groups.

Strike Force Alistair was established by the Organised Crime Squad and the NSW Crime Commission in July 2011, with assistance also provided by the Gangs Squad.

The strike force has been investigating the supply of guns, drugs and explosives to organised crime groups, with some of those items allegedly destined for outlaw motorcycle gangs.

Police said a "number of arrests" had been made.