The Ivory Coast international slammed home a fine drive to give City a second-half lead before Lampard and Clichy wrapped up all three points in the final 10 minutes, despite Eliaquim Mangala’s sending off.
However, City were left sweating over a potential injury problem suffered by Vincent Kompany, with the club captain limping off in the final minutes.
Southampton went into Sunday’s game flying high after a stunning start to the season, but were given a reality check in a comprehensive performance from Manuel Pellegrini’s side.
In-form striker Sergio Aguero was denied what appeared to be a clear penalty early on when he was fouled in the box by Jose Fonte, only for referee Mike Jones to caution him for simulation – much to the Argentinian’s bemusement.