Live explosive discovered at Sydney home

A live grenade has been discovered buried in a backyard on Sydney's north shore.

Australian Defence Force personnel were called to a house in Crows Nest on Friday afternoon following reports an explosive device had been uncovered during renovation work.

The explosive was identified as a 1970s smoke grenade and police say it was "live".

An exclusion zone was set up around the house until defence personnel took the grenade away for safe disposal.