SA bushfire flares up overnight

A bushfire threatened townships in South Australia's Flinders Ranges overnight as the blaze jumped containment lines.

The Bangor fire, which began last week during the state's heatwave, had been controlled but late on Wednesday night it broke containment lines and headed towards Napperby, Nelshaby and Telowie.

The Country Fire Service issued an emergency warning for residents, but on Thursday morning this changed to a watch-and-act advice.

"It's pretty much contained, generally freely burning in some areas within the containment lines," incident controller Dennis Turner told ABC radio.

"A few little spot areas of some concern to us but generally not too bad."