Sri Lanka's stand-in captain Upul Tharanga has been suspended for his team's next two matches in the Champions Trophy because of a "serious" over-rate offence in their first group B match against South Africa at The Oval.

Sri Lanka took more than four hours to bowl 50 overs, and match referee David Boon ruled they were short of the target by four overs, even after making time allowances. Tharanga had been filling in as captain for Angelo Mathews, who did not make it through a fitness test on the morning of the match, and received two suspension points for the slow over rate.

"Tharanga pleaded guilty to the offence and accepted the proposed sanction, so there was no need for a formal hearing," the ICC said. "As two suspension points equate to a ban from one Test or two ODIs or two T20Is, whatever comes first for the player, Tharanga has been suspended from his side's upcoming matches against India and Pakistan, while each of his players have received a fine of 60 per cent."

Tharanga admitted he had been warned on-field that Sri Lanka were falling well behind the over-rate. "I think we were too slow to change over between overs. The umpires had told us that we were lagging, after 10 overs that we were two overs behind. In the last few overs it's hard to catch up, because you need some time at the death. "

He was Sri Lanka's top scorer against South Africa, making 57 off 69 balls as they fell short by 96 runs in the chase of 300. His suspension now makes it even more imperative that Mathews is fit to face India at The Oval on June 8 as Sri Lanka aim to keep their tournament alive.

Speaking before the sanction against Tharanga was confirmed, Dinesh Chandimal, who would be the likely captain if Mathews wasn't fit, said he had been close to make the opening match.

"He just missed this game, but the thing is you can't risk playing the first game and making it worst," he said. "He's got four or five days before the next game to get ready."