A 27-year-old man was arrested in connection with the murder of an elderly couple at Plaas Poortjie Farm, Free State police said on Thursday.

"Two reservists constables were on patrol when they noticed a red Chevrolet with the registration numbers of the one police were on the look-out for," Captain Stephen Thakeng said.

The car was stopped on Seranyane Street in Kutloanong and the driver was arrested.

The couple, aged 65 and 60, were found murdered at their farm located between Senekal and Steynsrus on Wednesday.

Police said the farm generator apparently went off on Tuesday night and the woman went outside to investigate.

Someone stabbed her. She and her husband were then shot. The Chevrolet belonging to the couple's daughter had been stolen from the farm.