Manchester City boss Pep Guardiola says he knew "immediately" that his side had been wrongly awarded a penalty in Wednesday's 6-0 victory over Shakhtar Donetsk, but defended Raheem Sterling for not pointing out the error.

The England winger went down in the box in the 24th minute after kicking the turf as he shaped to shoot.

But referee Viktor Kassai pointed to the spot, believing Sterling had been felled by Shakhtar defender Mykola Matvyenko, and Gabriel Jesus stepped up to score City's second and the first goal of his hat-trick.

Guardiola appeared to motion on the touchline that he disagreed with the decision and later confirmed: "We realised immediately it was not a penalty."

However, asked whether Sterling should have made Kassai aware that he had not been touched by Matvyenko, Guardiola highlighted an incident from last season's quarter-final second-leg defeat to Liverpool, when Leroy Sane had a goal incorrectly ruled out for offside after the ball had come off Reds midfielder James Milner.

"He could do that [flag up the mistake], but last season Liverpool... Milner could say that the pass to the second goal in the 44th minute it was a legal goal," he said.

"But [referee Antonio] Mateu Lahoz didn't want to concede that goal, so that's why it happened, but he could do that, yes.

"We don't like to score a goal in that situation but [Sterling] didn't realise. The referee at the end realised. The Spanish referee Mateu Lahoz, he realised, he didn't want to concede.

"But in that situation [Sterling] didn't realise because he wanted to chip, caught the grass, goes down, it's not a penalty."

Guardiola, who added that he had never asked a player to intentionally miss a penalty following an incorrect decision, stressed the need for more help for officials, with VAR not due to be introduced to the Champions League until next season.

"VAR, where is it? The referees said a long time ago there must be help, because they want to make a good performance, they don't want to make mistakes," he said.

"But today the game is quick, it's fast. The players are more skilled in something.

"In the end there must be help, because it takes three, four seconds or 10 seconds for someone to say it's no penalty, carry on, go."

City's win put them three points clear of Lyon at the top of Group F with two matches left to play.