Bangladesh 320 (Mominul 77, Mahmudullah 66, Maharaj 3-92) and 49 for 3 (Morkel 2-19) need another 375 runs to beat South Africa 496 for 3 dec (Elgar 199, Amla 137) and 247 for 6 dec (Du Plessis 81, Bavuma 71, Mominul 3-27, Mustafizur 2-30)
Potchefstroom: South African fast bowler Morne Morkel took two wickets for no runs in the first over of Bangladesh's second innings on the fourth day of the first Test at Senwes Park on Sunday, but then suffered an injury likely to keep him out of the rest of the match.
Bangladesh were 49 for three at stumps after being set to make 424 to win. Rain fell during the tea interval and suspend play of he day.
Morkel took two for 19 before leaving the field with a side strain after bowling two balls of his sixth over.
Cricket South Africa media officer Lerato Malekutu said Morkel would be taken for scans on Monday and was unlikely to bowl again in the match.
Morkel's sensational start could have been even better because he was denied a third wicket because of a no-ball.
Morkel, bowling around the wicket, bowled Tamim Iqbal with his fourth ball, a superb delivery which straightened off the pitch and hit the off stump. Two balls later he won a leg before wicket decision against another left-hander, Mominul Haque, who made top score of 77 in Bangladesh's first innings.
After consulting batting partner Imrul Kayes, Mominul did not seek a television review of umpire Chris Gaffaney's decision - but replays showed the ball would have missed the leg stump.
Switching to over the wicket, Morkel uprooted the middle stump of Mushfiqur Rahim, Bangladesh's right-handed captain, with the second delivery of his next over. But a television check showed the bowler had over-stepped the bowling crease. A no-ball was called and Rahim was reprieved.
It was a world record 14th occasion on which Morkel had been denied a Test wicket because of a no-ball.
South Africa missed another chance when captain Faf du Plessis dropped Kayes at second slip off Kagiso Rabada when the batsman was on six. Kayes made 32 before he was caught behind off left-arm spinner Keshav Maharaj in the last over before tea.
Du Plessis (81) and Temba Bavuma (71) set up South Africa's second innings declaration on 247 for six with a fourth wicket partnership of 142 off 172 balls. The innings was interrupted for 47 minutes by a thunderstorm, which caused the tea interval to be delayed by an hour.
Part-time left-arm spinner Mominul claimed a career-best three for 27 as South Africa chased quick runs. He had taken only four wickets in 23 previous Tests. By contrast, Mehidy Hasan, Bangladesh's only front-line spinner, did not take a wicket and conceded 247 runs in 67 overs during the match - the third-highest number of runs conceded by a bowler without taking a wicket in a Test match.