Published: 2019-08-31 23:48:40 BdST
With unbeaten Liverpool playing Burnley in the evening kickoff, Pep Guardiola's side went above their great rivals at the top of the table on a day when West Ham United, Leicester City and Crystal Palace all won while Sheffield United fought their way back from two goals down to grab a point at Chelsea.
After four games, City have already registered twice as many goals and points as United. The result was never in doubt at the Etihad from the moment Kevin de Bruyne put them ahead in the second minute.
With Aguero keeping up his record of scoring in each of City's four league games and substitute Bernardo Silva netting with his second touch, it was business as usual for City, who lost French defender Aymeric Laporte with what looked like a serious injury.
De Bruyne was delighted with his strike, particularly after missing so much of last season with knee and hamstring injuries.
"I've just got to keep on going. Last year was last year, I have started this season well, I feel OK and the team is doing well," he said.
United failed to take advantage of their numerical superiority at Southampton where the home side played the final 17 minutes with 10 men after defender Kevin Danso was sent off for a second yellow card.
Although United took the lead through Daniel James, who registered his third league goal of the season with a fine strike, Danish centre back Jannik Vestergaard headed the equaliser on 58 minutes.
Southampton then held firm to frustrate the visitors under manager Ole Gunnar Solskjaer, who said two points from their last three games represented "a dip in results but not form".
The Norwegian also rejected suggestions Paul Pogba could leave the club before Monday's European transfer deadline.
"Paul Pogba will be playing for us," he said.
Third-placed Leicester continued their excellent start to the season with a 3-1 win over Bournemouth, with Jamie Vardy involved in all the home team's goals.
The striker scored twice and made a third for Youri Tielemans to complete a memorable week in which it was announced his wife is pregnant for the fifth time.
Chelsea manager Frank Lampard looked close to securing his first home win of the season after Tammy Abraham scored twice in the first half but the promoted visitors showed plenty of fight to snatch a point with a strike from Callum Robinson and a late own goal from Kurt Zouma.
At Selhurst Park, Jordan Ayew scored Crystal Palace's first home goal of the season in the 1-0 win over Aston Villa although the game ended in controversy after the visitor's late equaliser was ruled out for an apparent dive by Jack Grealish.
West Ham's Sebastien Haller scored his third goal in two games as the Hammers beat Norwich City 2-0 at London Stadium while bottom side Watford, who had lost their first three games, eased some of the pressure on manager Javi Gracia by scraping a point in the 1-1 draw at Newcastle United.