Bloemfontein: South Africa sneaked a four-run win over Sri Lanka on the Duckworth/Lewis method in a rain-affected third one-day international on Tuesday to clinch the five-match series 3-0.South Africa were 179-5 after 34 overs chasing Sri Lanka's 266-9 when rain came down at Chevrolet Park.Umpires called the game off about an hour and 20 minutes later, handing South Africa a narrow victory and first series win under new skipper AB de Villiers.De Villiers was 39 not out at the end and Albie Morkel 7 not out, but Faf du Plessis's career-best ODI score of 72 from 99 balls had pushed South Africa within reach of victory. Du Plessis' innings was crucial after Lasith Malinga (2-20) struck twice and the home team slipped to 113-4."I would have liked the game to go to the end," De Villiers said, "but I am proud of the boys. We pulled it back with the ball and were solid with the bat."Sri Lanka's competitive total was earlier set up by a second successive half-century by Upul Tharanga in a 94-run opening stand with captain Tillakaratne Dilshan (33).Sri Lanka couldn't capitalize on their strong start, however, as Dilshan, Kumar Sangakkara (38) and Dinesh Chandimal (36) didn't go on to make big scores when well-set. Nuwan Kulasekara hit a quickfire 40 down the order but the tourists were reined in when a 300-plus score was possible.South Africa spinners Robin Peterson and JP Duminy had a wicket each to remove the openers, while fast bowler Morne Morkel finished with 2-65.The Sri Lankans were still unfortunate not to have the chance to see the game through and apply late pressure on the home team, who still needed 88 runs off 16 overs when the weather intervened."We're definitely disappointed to lose the series like this," Dilshan said. "We had a great chance to win today, with Lasith (Malinga) still having five overs with almost 90 runs to go. We'll try to finish strongly in the last two games."Tharanga made a rapid start, crashing five fours and two sixes in his 58 from 65 balls before Peterson had him caught off a top-edged sweep by Colin Ingram. Dilshan fell eight runs and two overs later.Sangakkara and Chandimal added 52 for the third wicket but their stand was ended with a Du Plessis direct hit from backward point to run out Sangakkara.Sri Lanka slipped from a strong position at 154-2 to add just 112 more runs in the last 20 overs, despite late rallies from Nuwan Kulasekara and Kosala Kulasekara, who made 19 from 20 balls.Malinga fired out Graeme Smith and Ingram in a deadly opening spell and recalled opener Alviro Petersen fell for 17 trying a reverse sweep off Dilshan to leave South Africa 52-3.Du Plessis and Duminy rebuilt with their 61-run partnership until Duminy was given run out for 25 when Nuwan Kulasekara threw down the stumps.TV replays appeared to show Duminy just home and the surprise decision by third umpire Billy Doctrove left South Africa's players shaking their heads in bewilderment and coach Gary Kirsten clearly angry. In his disappointment, Duminy took a long time to leave the field.Du Plessis hit seven fours in his third ODI half-century and even though he was also run out after struggling with cramp â the fifth run-out in the match â No. 6 De Villiers dragged South Africa above the required run rate with three fours in his 39 from 36 deliveries.It was just enough for a fifth ODI series win in their last six for the Proteas and sent Sri Lanka to a fifth straight loss in limited-overs contests.