Restored to the side after overcoming a groin problem, Haaland opened the floodgates by heading home in the final minute of the first half.

Jack Grealish doubled City's lead before Haaland's acrobatic overhead strike took his tally to 44 goals in a remarkable debut season with the English champions.

But the Norwegian was denied another hat-trick as he had been substituted by the time Julian Alvarez scored City's fourth from the penalty spot.

Sekou Mara had pulled a goal back for Southampton by then, but they remain rooted to the foot of the table and four points adrift of safety.

Pep Guardiola was true to his word that he was not thinking about Tuesday's Champions League quarter-final, first leg against Bayern Munich as Haaland's return was the only change from the side that thrashed
Liverpool 4-1 last weekend.

But the visitors failed to hit the same heights for the first 45 minutes and could have been punished against a side with more firepower than the Saints.

Kamaldeen Sulemana had the best chance to give Ruben Selles' men a shock lead when he beat Kevin De Bruyne to the ball and sprinted clear into the City half.

However, Nathan Ake did well to narrow the angle before Ederson raced off his line to divert the ball to safety.

Haaland was more forgiving than he normally is by giving Southampton a let-off as he powered a header wide at the back post from a deflected cross.

But he made no mistake with a similar opportunity just before half-time when he stooped to meet De Bruyne's cross.

City went through the gears after the break as an eighth consecutive win in all competitions kept Guardiola's men in the hunt for a treble of trophies.

Grealish is enjoying his best form since a £100 million ($124 million) move from Aston Villa in 2021 made him the Premier League's most expensive ever player at the time.

He fired in at the second attempt after his first effort was saved by Gavin Bazunu.

Grealish turned creator for the third as his cross was finished in spectacular fashion by Haaland with an overhead kick for his 30th Premier League goal of the season.

That was the striker's final touch as he then made way for Alvarez for the final 20 minutes with one eye on Bayern's visit in midweek.

Mara briefly gave the home support something to cheer when he steered home Moussa Djenepo's cross.
But City restored their three-goal cushion just three minutes later when De Bruyne was bundled over inside the box.

The Belgian stood aside to allow Alvarez to fire home his 14th goal of the season despite largely playing second fiddle to Haaland.

Liverpool have tended to be City's title rivals in the Guardiola era.

But they will be hoping for a favour from their old foes on Sunday when Arsenal go to Anfield hoping for their first away league win against Liverpool in 11 years.