Convicted B.C. serial killer Robert Pickton is in critical condition and undergoing surgery after he was assaulted by another inmate in a Quebec prison on Sunday.

The Correctional Service Canada (CSC) confirmed in a statement Tuesday that Pickton was the victim of a "major assault" at the maximum-security Port-Cartier Institution.

Two sources, including one police source, told Radio-Canada that Pickton is between life and death.

Pickton was taken to a hospital for treatment and the assailant is in solitary confinement according to the Quebec provincial police, the Sûreté du Québec (SQ), which is investigating.