A fire burning near Oxford Falls in Sydney's north that was considered out of control earlier today has been downgraded from Emergency to Advice.

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.

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