The return clash at the Etihad Stadium next month should now be a formality for City, whose remarkable challenge on four fronts continues virtually unhindered.

Even manager Pep Guardiola, who refuses to look much farther ahead, believes this particular hurdle is as good as cleared.

"It's an amazing result for the last 16 of this competition," the former Barcelona and Bayern Munich boss said.

"The Champions League is (about playing) 180 minutes but we are almost there. I'm not saying it's done because in football anything can happen but it's an amazing result.

"We were clinical and I am delighted with the performance. They were four amazing goals."

After surviving a couple of early scares, City soon took control with three goals in a blistering spell between the 14th and 23rd minutes.

Gundogan opened the scoring with a near post header before Silva controlled on his chest and volleyed home, and Aguero lashed in a shot from outside the area.

Gundogan added the fourth with a fine curling shot after 53 minutes and he almost claimed a hat-trick in the latter stages when Tomas Vaclik saved from close range.

"He's a guy with special qualities," Guardiola said of the German, whose first season at City was marred by injury.

"He's amazing with a good sense of goal.

"When I see him play I realise how we missed him last season. He is a special player with a lot of personality. He doesn't feel pressure, he's a top player."

City next play when they face Wigan in the fifth round of the FA Cup on Monday with the Carabao Cup final against Arsenal coming up the following weekend.

Guardiola, whose side are 16 points clear at the top of the Premier League, said: "Overall I'm delighted but now we prepare for Wigan."

- PA