Former Australian captain Steve Waugh has lauded Indian skipper Virat Kohli for "calming down" the crowd which booed Steve Smith in their World Cup clash in London, calling the gesture a "class act".

Waugh, one of the toughest and most successful captains of all time, said he was impressed by Kohli's action of asking the crowd to not boo Smith, who is continuing to cope the fans' ire after returning from a one-year ban for ball-tampering.