Two men seeking shelter on a golf course during a storm were struck by lightning - which killed one of them - on Tuesday afternoon in the Free State.

They were working on a construction site on the golf course in Parys.

ER24 spokesman Russel Meiring said one of the men, in his 40s, had been moved to a nearby home when paramedics arrived.

"Paramedics assessed the patient and found that he had he showed no signs of life. Nothing more could be done for him and he was declared dead.

"A second man who had been with the deceased at the time, and also struck, was assessed and found to have escaped injury," he said.

The South African Weather Service warned people to take shelter earlier on Tuesday as severe thunderstorms were forecast for Mpumalanga and the Free State.

People exposed to lightning were cautioned not to take shelter under trees, power lines or near steel structures.