Ivory Coast defender Eric Bailly has become the first Manchester United player to score an own goal in the Manchester derby in the Premier League era.
The home side found themselves trailing when the Ivorian tried to clear a cross into the penalty area by Joao Cancelo, who flicked a return effort in from the left edge.
Victor Lindelof had cleared the first attempt by the Manchester City man only for Bailly to put the ball into his own net in the seventh minute as he attempted to make a further clearance.
Bernardo Silva added the second for the Premier League champions in added minutes of the first half, as Pep Guardiola's men took a 2-0 lead into the half-time break.