People living north of Hawker in the Flinders Ranges have been told to enact their bushfire plan or leave the area as the South Australian Country Fire Service (CFS) fights an out-of-control blaze.

The CFS issued an emergency warning about 3:20pm on Friday but later downgraded it to a Watch and Act alert.

It warned the blaze was near Yappala Road, Wonoka Creek Road and Dairy Farm Road, and was travelling in a north-easterly direction towards Wonoka Plains.

The CFS urged residents to enact their bushfire plans or leave the area as the blaze posed a risk to their safety.

"If you are not prepared, leave now. Only leave if the path is clear to a safer place," the alert stated.

"The fire is uncontrolled and burning in scrub and conditions are continually changing."

The CFS also advised people not to enter the area affected by the fire as the roads may not be safe.