Vienna: Austria's Justice Ministry says two nurses convicted in 1991 of killing at least 20 elderly patients at a Vienna hospital will be released from prison next month.

Officials say they have approved the conditional release of 49-year-old Waltraud Wagner and 46-year-old Irene Leidolf.

Prosecutors say the pair led a group of four nurses dubbed "angels of death" for killing old and chronically ill patients with drug overdoses or by forcing water into their lungs.

Wagner and Leidolf were convicted of murder in the slayings from 1983 to 1989 at Vienna's Lainz Hospital. Both were sentenced to life in prison.

Officials said Thursday they will be released early for good behavior. Their accomplices were freed several years ago.