Pakistan's medium pacer Hasan Ali took two wickets off successive deliveries as South Africa reached 26-2 at tea on the second day of the second Test in Rawalpindi on Friday.
Hasan had opener Dean Elgar caught behind for 15 with the fifth delivery of his third over and next ball bowled Rassie van der Dussen for a duck as players walked off for the break.
At tea Aiden Markram was unbeaten on ten as South Africa still trail Pakistan's first innings total of 272 by 246 runs.
Earlier, South African paceman Anrich Nortje grabbed his third five wicket haul with 5-56 to restrict Pakistan's total.
The 27-year-old took the prized wicket of Babar Azam off the second ball of the day before wrapping Pakistan's innings half an hour before tea.
Nortje bowled with fire and aggression on a flat, brownish Rawalpindi stadium pitch which is suited more to spin.
Keshav Maharaj finished with 3-90.
Despite South Africa's controlled bowling, allrounder Faheem Ashraf played a brilliant knock of 78 not out studded with 12 hits to the boundary -- his fourth Test half century.
Pakistan had looked to Azam and Fawad Alam to build on their partnership of 123 after rain cut short the first day to 58 overs.Azam slashed at a short delivery from Nortje and was smartly snapped head high by Faf du Plessis in the second slip for his overnight score of 77.
Azam's dismissal was the start of a mini-collapse which saw Pakistan lose two wickets in the space of 34 balls with the addition of just four runs after resuming at 145-3.
The other overnight batsman Alam was run out after he tried to steal a quick single with a push to cover but failed to beat a direct throw from Temba Bavuma at the non-striker's end.
Alam could only add three to his overnight score of 42.
Azam, who was looking set for his sixth Test century, had hit 12 boundaries off 127 balls.
Ashraf then added 41 with Rizwan but once South Africa took the second new ball Nortje struck again, having Rizwan caught off a miscued hook for 18.
Pakistan lead the two-match series 1-0.
