MUMBAI: Jos Buttler scored another Twenty20 century to power Rajasthan Royals to the top of the Indian Premier League table but Friday's 15-run win over Delhi Capitals was overshadowed by farcical protests over an umpiring decision in the final over.

England batter Buttler smashed 116 off 65 deliveries for his third hundred in this season's IPL as Rajasthan posted 222-2 after being put in to bat first at Mumbai's Wankhede Stadium.

Delhi needed 36 off the final over and their hopes of an unlikely victory was fanned when Rovman Powell clobbered fellow West Indies cricketer Obed McCoy for three consecutive sixes off the first three deliveries.

The third six came off a high full toss from the left-arm fast bowler and the on-field umpires ruled the delivery was not above the waist and did not call a no-ball, which would have given Delhi an extra run and a free-hit on the next ball.

The Delhi dugout appeared upset that the on-field officials did not seek help from the television umpire to check the height of the delivery with captain Rishabh Pant seen waving to his two batters to leave the field.

The batters started walking towards their dugout but relented after being spoken to by the umpires. However, chaos ensued when Pant sent assistant coach Pravin Amre on to the field to talk to the officials.

Buttler seemed infuriated by Pant's behaviour and walked up to him to have a word.

The break did not help Delhi when play resumed with McCoy conceding just two more runs off the final three deliveries with Powell getting out on the last one.

Delhi assistant coach Shane Watson said what happened in the last over was "disappointing" and umpires' decision has to be accepted.

"It wasn't right, but what happened with us was also not right," Pant said at the presentation when asked about his move to send Amre to talk to the umpires on the field. "It was just the heat of the moment, can't do much about it.

"I thought that no-ball could have been precious for us. I thought we could have checked that no-ball, but (that is) not in my control. Yes, disappointed, but can't do much about it."