Former Smallville actress Allison Mack admits racketeering charges related to sex cult

American actress Allison Mack has pleaded guilty in a case involving a cult-like group based in upstate New York who allegedly recruited sex slaves for its spiritual leader.

Mack entered her plea to racketeering charges on today, shortly before federal jury selection was scheduled to start in Brooklyn federal court.

The trial is expected to detail sensational allegations that the group, called NXIVM, recruited sex slaves for its spiritual leader, Keith Raniere.

Prosecutors accused Mack, who starred in television show Smallville, of helping Raniere recruit women to a secret sub-society within the group.

Authorities say the women were branded by a surgical tool with a symbol that resembled Raniere's initials. Mack has said in an interview that the group emphasised self-discipline and self-empowerment and she likened the branding to getting a tattoo, but cooler.

The defense says the women were never abused.