Mayank Agarwal saluted the "tremendous" Virat Kohli after the India captain made his highest Test score on a punishing day two for South Africa in Pune.

Kohli crafted 254 not out with support from Ajinkya Rahane (59) and Ravindra Jadeja (91) as India racked up a mammoth 601-5 declared on Friday.

The skipper had not reached three figures in the longest format this year, but posted a seventh double-century and also passed 7,000 Test runs with a masterclass before the tourists were reduced to 36-3 at stumps as India eye an unassailable 2-0 lead.

Agarwal, who scored a hundred on day one, hailed Kohli after he made the Proteas bowlers toil - hitting two sixes and 33 fours in a stunning knock.

"It was a top-class knock from him. To get 250 is no joke and the way he's batting is just tremendous." the opener said.

"The positivity he gets, the intent he gets is fabulous. His records and his scores and the way he's playing shows everything we all need to see."

Agarwal says the rapid rate in which Kohli and Jadeja scored during a fifth-wicket stand of 225 could prove to be vital.

He added: "It's put us in the driving seat and it's not just the amount of runs, it's the pace that the runs have come that has made a huge difference. It's giving us extra time, that extra session and a half that can become very crucial."

South Africa interim director Enoch Nkwe pointed the finger of blame at the seam bowlers at the end of a gruelling second day.

"We've only got ourselves to blame this morning. We thought the conditions were conducive to seam bowling, we just didn't hit our straps." Nkwe said.

"We bowled a little bit too wide and didn't test the Indian batters enough and when we do that we just allow the batters to get in and we need to learn tight lines for a longer period of time."