An 80-year-old woman dubbed Canada's "Black Widow" has been arrested after breaching the conditions of her release by using the internet at a library in Halifax, Nova Scotia.

A police spokeswoman said Melissa Ann Shepard was arrested Monday. Shepard gained notoriety for killing and poisoning several men who were her intimate partners and has a lengthy history of offences.

The arrest comes less than a month after Shepard was released from prison. She served just under three years for spiking newlywed husband Fred Weeks' coffee with tranquilizers in 2012. Weeks survived after falling ill during a trip to Newfoundland.

Shepard was convicted of manslaughter and served two years in prison in the early 1990s in the death of her second husband, Gordon Stewart, whom she drugged and ran over twice with a car.