The Country Fire Service says three homes have been lost as a string of bushfires burn across South Australia.

Three homes have been destroyed in the Barossa Valley and fire crews are battling to save more as a series of major bushfires continue to burn across South Australia.

The Country Fire Service said two homes and a cottage had been destroyed in a fire burning out of control at Eden Valley, northeast of Adelaide.

CFS crews were actively protecting other properties with the blaze burning through more than 4000 hectares of grassland in a matter of hours.

It was being tackled by ground crews as well as two helicopter water bombers, three fixed wing aircraft and an aircrane but was running strongly in steep terrain and had jumped a number of local roads.

Other areas causing most concern on Friday were a complex of fires at Renmark, in the state’s Riverland, and a major blaze at Bangor in the lower Flinders Ranges.

An emergency warning had also been issued for a fire at Owen, north of Adelaide, but the CFS said crews were increasingly confident the worst had passed.

At Renmark the fires had destroyed more than 60,000 hectares of scrub and remained out of control.

They were burning towards Cooltong and Renmark West where a number of people had left their homes.

Meetings were to be held in the area to inform residents on the emergency.

The fire at Bangor also remained out of control as it raced through 3560 hectares of forest.

There were fears for some properties in the area as it burnt towards the Wirrabara and Laura townships.

With all the major fires the CFS said the big concern was the changing conditions with winds rising and shifting as a cool change swept across the state.

Thunderstorms were also forecast to accompany the change with the CFS expecting more fires to be sparked by lightning strikes.

Across the state the CFS had about 700 firefighters on the ground tackling more than 20 fires.