South Africa beat hosts Sri Lanka by a convincing 32 run margin in a rain-shortened seven-over-a-side World Twenty20 group C match on Saturday.
South Africa were good with both bat and ball as their pacemen never allowed the Sri Lankan batsmen to chase a daunting 79-run target.
Skipper AB de Villiers smashed two sixes and a boundary during his 13-ball 30 while Hamshim Amla (16) and Faf du Plessis (13) were the other main run contributors in a total of 4-78 after South Africa lost the toss.
Sri Lanka were without their ace spinner Ajantha Mendis, who took 6-8 in their win over Zimbabwe but suffered a side strain.
Heavy rain delayed the start by two and a half hours for a sell-out 35,000 crowd at Hambantota.
The Sri Lankans were never in the hunt, losing star duo Tillakaratne Dilshan (nought) and Mahela Jayawardene (four) in the first two overs.
Dilshan Munaweera and Kumar Sangakkara made 13 each in a total of just 5-46.
Dale Steyn was South Africa's best bowler with 2-10.
De Villiers said his men were ready for the next round.
"Beating Sri Lanka is nice because they are one of the top teams and now we are ready for the Super Eights, we didn't take anything for granted and it was nice to win," said the South African captain.
Jayawardene said it was tough with fewer overs: "It is always tough in a rain-reduced match. We were without Mendis because we didn't want to take risk with important matches coming up.
"We must improve our fielding."
South Africa, who finished top of the group, and Sri Lanka qualified for the Super Eight rounds. Both had beaten Zimbabwe in their opening matches.
Sri Lanka will be in group one of Super Eights while South Africa will be in group two, regarded as the group of death with India, Australia and Pakistan likely to be the other teams.