Manchester City were left with a healthy eight-point lead at the top of the Premier League after second-placed Manchester United suffered a 1-0 loss away to champions Chelsea hours after the leaders saw off Arsenal 3-1 on Sunday.

United manager Jose Mourinho, a former title-winning boss with Chelsea, saw his latest visit to Stamford Bridge end in defeat courtesy of Alvaro Morata's 55th-minute header that ended a run of six game without a goal for the Spain striker.

Victory left Chelsea fourth, nine points off the summit.

Earlier, City were impressive against the Gunners, with Kevin De Bruyne firing Pep Guardiola's men into an early lead at the Etihad before Sergio Aguero made it 2-0 afrom the penalty spot early in the second half.

Alexandre Lacazette pulled a goal back for the Gunners but Gabriel Jesus put City 3-1 up in the 74th minute despite a suspicion of offside, with Arsene Wenger's Arsenal now 12 points behind City.

"The physical level is very good but the decisions," veteran manager Wenger told Sky Sports.

"The third goal, at 2-1 we are in the game and he (referee Michael Oliver) gives a clear offside goal. And, of course, that kills the game for us.

"They are a top team but that (bad decisions) makes it even more difficult for you."

However, City counterpart Guardiola had no truck with suggestions his side had been fortunate to win.

"We won in the best way and we deserved by far the victory," said Guardiola after City backed up their midweek Champions League win away to Napoli with another commanding victory.

"We fought in the bad moments, when we were tired, mentally we were stable. I was pleased with the performance. The third goal helped us to win the game.