The Rural Fire Service has lowered the alert level for the blaze which began as a hazard reduction burn in Oxford Falls.

A fire is burning out of control in Sydney's north, with residents and a nearby aged care warned to prepare to act.

A fire in Sydney’s northern beaches that firefighters had warned was threatening lives has been downgraded after conditions eased. The NSW Rural Fire Service had earlier on Saturday warned people in the Cromer Heights area near Oxford Falls Road that their lives were at risk and that they should immediately seek shelter.

An out-of-control fire is burning near Oxford Falls in Sydney's north. Firefighters are at the scene trying to control the blaze, which is burning east towards Cromer Heights.

Residents are being urgently evacuated from Sydney's Northern Beaches as firefighters battle an out-of-control hazard reduction burn.