Alastair Forsyth of Scotland and England's Andrew Butterfield each shot 66 to join the South African quartet of Tim Clark, Ashley Roestoff, James Kingston and Des Terblanche in second place at 6-under.
Retief Goosen, whose U.S. Open victory helped him to the European Tour's Order of Merit (money) title last year, also finished the first 18 holes without a bogey. The South African carded a 67 for a share of eighth place with Zimbabwe's Marc Cayeux and Simon Dyson of England.
Goosen captured the South African Open at Randpark Golf Club in 1995.
Pettersson, the 2000 European Amateur champion and a four-time All-American at North Carolina State, notched five birdies on his front side - the back nine at Durban - then pushed into the lead with three birdies over his final five holes.
'I had four weeks off and didn't play much golf, so I was pleasantly surprised,' he said.
The 24-year-old Swede is off to a sizzling start on the 2002 European Tour schedule, which actually began in late November 2001. After tying for fourth place at the BMW Asian Open in Taiwan, he moved on to the Omega Hong Kong Open, where he finished solo fifth.
'I was quite pleased finishing 61st on the Volvo Order of Merit last season but I had a good amateur record and set high goals for myself,' said Pettersson, whose best finish in his rookie year of 2001 was second at the Argentina Open. 'I want to win and take it from there.'
Pettersson, currently third on the 2002 Order of Merit, is looking to become the second Swede in three years to win this title. His countryman, Mathias Gronberg, triumphed at Randpark in 2000.
Clark, who by coincidence was Pettersson's roommate for a year at N.C. State, has fought back after missing almost all of last year with a wrist injury that required surgery. The Durban native earned a spot on last year's PGA Tour in the U.S. by finishing third on the Buy.Com Tour money list in 2000.
'It doesn't hurt now, but it's not 100 percent right,' Clark said of his wrist. 'I've got a medical exemption for this year and will go back to the States later this month to play in the AT&T (Pebble Beach National Pro-Am).'
Clark posted seven birdies Thursday and his lone bogey came at the 17th, his eighth hole of the day. His 66 matched the score he shot to finish first in Tuesday's qualifying round.
The 1999 British Open champ, Paul Lawrie, whose latest win came with a dramatic 40-foot birdie putt from the Valley of Sin at St. Andrews in the Dunhill Links Championship in October, was part of an eight-way tie at 4-under 68.
Three-time South African Open winner Ernie Els (1992, '96, '98) was shaky with two birdies and three bogeys Thursday. He finished nine shots off the pace, in a big group that included defending champion Mark McNulty.
Full-Field Scores from the Bell's South African Open