Lightning struck 150 people gathered at a festival north of South Africa's capital Pretoria, killing two, local health services said on Sunday.

The incident occurred on Saturday night near the village of Mathibestad, about 70 kilometres of Pretoria, where a traditional celebration is held every year.

The North West health department said 150 patients came to a health clinic after being struck by lightning during the event, adding that two died and 13 were in critical condition and transferred to another health facility.

Storms are frequent in this part of South Africa during the current summer season in the southern hemisphere.