Nagpur: Imran Tahir grabbed three quick wickets to reduce India to 108/5 in their second innings at tea on Day 2 of the second Test in Nagpur.
But the hosts had managed to swell their lead to 244 with five wickets still in hand.
The target already looks to be well beyond South Africa, who were knocked over for a measly 79 in their first innings earlier in the day.
Opener Murali Vijay fell cheaply to Morne Morkel before Shikhar Dhawan and Cheteshwar Pujara steadied the ship.
Pujara made an aggressive 31 off 45 balls before he was castled by JP Duminy.
Dhawan and skipper Virat Kohli took the score to 97 before India lost three wickets in the space of 11 runs to Tahir.
Dhawan was caught behind off a reverse sweep and then Kohli tried to take on Tahir, only to hole out to long off.
Ajinkya Rahane also fell for 9 in the last over before tea, playing a loose drive and edging the ball to Duminy at short third man.
Rohit Sharma and Wriddhiman Saha were at the crease at tea as India looks to build a lead of over 300.
Ashwin, Jadeja destroy South Africa for pitiful 79
Ravichandran Ashwin and Ravindra Jadeja ripped South Africa to shreds on Day 2 of the third Test in Nagpur, dismissing the visitors for a sorry 79.
Ashwin finished with figures of 5/32 while Jadeja ended with 4/33.
It was the lowest total ever made against India in Test cricket.
India were on 7/0 at lunch in their second innings after having grabbed a handy first innings lead of 136.
With the pitch likely to deteriorate further, India are well on course to clinch the series.
Resuming at 11/2, the visitors lost three wickets for just one run to be reduced to a dismal 12/5.
It was the lowest score at which South Africa had lost half their side in Test history.
Dean Elgar was the first to go in the very first over of the day, chopping a wide delivery from Ashwin onto his stumps for 7.
Skipper Hashim Amla's poor form continued as he fell to Ashwin for just 1.
Jadeja then joined the party by grabbing the prize scalp of AB de Villiers for a duck.
Faf du Plessis had made 0,1 and 0 in the first two Tests and did better this time but only slightly. He was castled by Jadeja for 10.
JP Duminy was the only batsman to offer some resistance, making 35.
Duminy used his feet to the spinners and struck Jadeja for two sixes.
He was eventually dismissed by the third member of India's spin troika, Amit Mishra.
