Virat Kohli marked his 35th birthday with his second century of the World Cup while Shreyas Iyer scored a fifty as India posted a formidable 326-5 against South Africa in a clash between the tournament's top two teams at the Eden Gardens on Sunday.

Kohli's unbeaten 101 contained 10 fours and left him level with Indian great Sachin Tendulkar on 49 one-day international hundreds as he continued his superb form by taking his tally past 500 runs in the tournament.

He dropped anchor in a third-wicket partnership of 134 with Iyer, who made 77 with seven fours and two sixes, before getting to his ton in the 49th over after India went past 300 runs on a slow Kolkata wicket.

India elected to bat first after winning the toss and took advantage of some wayward pace bowling by Marco Jansen to make a blazing start but skipper Rohit Sharma fell for a 24-ball 40 as he looked to launch first-change Kagiso Rabada over mid-off.

After reaching 91-1 in the powerplay, the hosts lost opener Shubman Gill (23) to an unplayable delivery from Keshav Maharaj in the 11th over as South Africa brought the run-rate under control with spin.