Henrik Stenson opened a four-shot lead at the South African Open with a second-round 65 before play was suspended for the day because of an electrical storm with much of the field yet to finish.

Stenson's 7-under 65, to go with his opening 66, put him at 13 under, ahead of Swedish compatriot Magnus Carlsson, who shot a 67 on Friday to move to second at 9 under.

First-round leader Merrick Bremner of South Africa was also at 9 under but still had four holes to play when they were called in for lightning at the Serengeti Golf and Wildlife Estate.

Seeking a first tournament win in three years - and first on the European Tour in five years - Stenson had five birdies and an eagle.