First Test, Centurion (day one, stumps):
Venue: SuperSport Park Date: 16-20 December Time: Play resumes 0830 GMT Coverage: Live on Sky Sports; reports and scorecards on BBC website
Morkel took his 100th Test wicket during the day
South Africa's fast bowlers reduced India to 136-9 on the rain-hit first day of the opening Test in Centurion.
Morne Morkel took 4-20 and Dale Steyn 3-34 to back their captain Graeme Smith's decision to bowl first.
After a rain delay of more than four hours, Virender Sehwag went for a duck in the third over but the real damage came after tea when six wickets fell.
Sachin Tendulkar (36) and Mahendra Singh Dhoni (33 not out) offered some resistance before bad light ended play.
"It's most important for a fast bowler that you don't forget your aggression - give the batsmen a bit of chin music, as they say, and it was nice to see the ball fly through," Morkel commented.
"For the batsmen, all the build-up about how the pitch will play is in the back of the mind and they're not sure whether to play back or forward. We were able to find the right lengths to create that doubt.
He added: "My strength is using my bounce. I don't get a lot of swing, but I also tried to bowl back-of-a-length and the batsmen were tentative, not knowing whether to play back or come forward."
Torrential rain washed out the morning session, and it wasn't until mid-afternoon that the toss was made.
Smith's decision to bowl was soon vindicated, as Sehwag's mistimed cut was taken by Hashim Amla at third man.
Morkel then took the wickets of Gautam Gambhir and Rahul Dravid in quick succession, but Tendulkar offered some resistance with brisk runs either side of tea.
However, the course of the day was decided when three wickets fell in three overs shortly after the interval.
VVS Laxman and Suresh Raina were both dismissed for single figures before Tendulkar succumbed, becoming Steyn's third victim when he was rapped on the pads plumb in front of his stumps.
Harbhajan joined Dhoni to take the Indians past 100 with a partnership of 39, but the off-spinner was run out going for a second run after dropping his bat.
Two further wickets fell to Morkel, but Dhoni and debutant Jaidev Unadkat were there at the close as bad light curtailed a day that featured only 38.1 overs.
India, who have recorded only one victory in 12 Tests in South Africa, are hoping to record a maiden series win in the country and consolidate their place at the top of the ICC Test rankings.
They sit 13 points above their opponents, who can draw level at the top with a 3-0 series victory.
"It was a damp wicket, very difficult to bat on and they bowled in good areas," said Harbhajan.
"We can come back. We have also got the bowlers to do damage. It's going to be important for us not to let them get too far ahead."