Manchester City manager Pep Guardiola hailed club-record signing Jack Grealish following his memorable Champions League debut, while lauding the ruthlessness of his team in their 6-3 rout of RB Leipzig.

Grealish – who arrived from Aston Villa in a reported £100million deal during the previous transfer window – scored in City's victory over visiting Leipzig in Manchester on Wednesday.

The England international teed up Nathan Ake for City's 16th-minute opener before scoring a goal of his own approaching the hour-mark midweek.

Grealish became the first Englishman to both score and assist on their Champions League debut since Manchester United great Wayne Rooney against Fenerbahce in September 2004.

"Hopefully it can be the first of many," Guardiola said of Grealish post-match. "I have the feeling that every day he is playing better, and I am pretty sure he will be better in the future.

"His contribution was again high, good. I am delighted with his game."

Christopher Nkunku scored a hat-trick for Leipzig, but Premier League champions City were not to be denied on a wild European night.

Riyad Mahrez, Joao Cancelo and substitute Gabriel Jesus were also on target for City, who benefited from Nordi Mukiele's own goal following Ake's opener.

City have won 50 of their 91 Champions League games (D16 L25) – becoming the second fastest team to 50 wins in the tournament's history after Real Madrid in 2003 (50 wins in 88 games).

"Of course, I am delighted and happy and thank you to these incredible players we have. It was a really tough game," said Guardiola, who took charge of his 300th match as City manager across all competitions (W219 D36 L45) and the 750th fixture of his career (W547 D113 L90).

"The first game at home it was important to win and we scored six goals. Seventeen goals in the last four games is nice to give to them. Now rest and prepare for Southampton. Nine goals in one game so it is nice for all the people watching.

"A team like RB Leipzig never gives up. They have a clear idea. They attack inside, they put a lot of players inside. They don't have the problem of losing the ball because when they lose the ball they make quick transitions.

"When we have the ball they are there to press you. At the same time when you can regain the ball, pass back and switch play a little bit, you always have a chance to run and score a goal.

"I think the game was tight. We were fortunate that when they scored we were able to score immediately.

"I saw the game against Bayern Munich, they made it 1-2 and Bayern Munich suffered because of the counter-attack. It is an interesting team.

"They have played like this since Ralf Rangnick arrived. They really play. It is one of the best teams in Germany. That is why I am incredibly satisfied with the players for the first victory in the group stage."