Manchester United will take a healthy lead to the Stade Geoffroy-Guichard for next week’s second leg after Zlatan Ibrahimovic’s hat-trick, sealed by a late penalty.

Manchester United 3-0 St-Étienne: Europa League – as it happened Read more

This took the Swede to 23 goals in his debut United campaign, the most since Robin van Persie’s 30 in the 2012-13 season.

Ibrahimovic’s opener was a fortunate strike from a free-kick, which was followed up with a tap-in after the break before his spot-kick beat Stéphane Ruffier.

This hands a clear advantage to José Mourinho’s side, though St-Étienne might have made United pay for slack defending throughout, an example being when Nolan Roux should have grabbed an away goal near the end but chipped over.

Mourinho made two changes from Saturday’s 2-0 win over Watford. Out went David de Gea, who was a substitute, and Henrikh Mkhitaryan, who reported ill, and in came Sergio Romero and Marouane Fellaini.

As expected Paul Pogba lined up against his elder brother Florentin, who was named in defence by Christophe Galtier.

Just before kick-off a raucous travelling support made their section a sea of red and green and set off flares, a few of which were hurled on to the pitch. The smoke from these lingered and the Les Verts faithful were in loud voice as the match began.

A first scare for United came when a loose Eric Bailly pass allowed the French side to attack via Romain Hamouma, who drew Romero out of his goal but could not capitalise.

Facebook Twitter Pinterest The Pogba family in the stands at Old Trafford Photograph: BT Sport

As they were facing France’s sixth-placed side at home, United could expect a first-leg win that would go a fair way to helping progress to the last 16. The 19 goals conceded by Galtier’s team in Ligue 1 is the second lowest so Mourinho knew his side would need patience to break the visitors down.

In fact, the wait lasted only 15 minutes. United lined up in a 4-3-3 that had Pogba on the left of the midfield trident and it was the No6 who initiated the attack from which United opened the scoring, by spraying a diagonal to the left.

When the ball came infield to Ibrahimovic, Jordan Veretout challenged and the referee, Pavel Kralovec, blew for a free-kick. Up stepped Ibrahimovic; his low shot hit Vincent Pajot in the wall, wrong-footed the goalkeeper Ruffier and had just enough pace to prevent Loïc Perrin clearing off the line.

From this breakthrough United dominated in passages with a mix of short and longer passes. Antonio Valencia may have been told to hit high balls and Fellaini posed problems when he roved forward to present a target.

When Ander Herrera missed a tackle on Hamouma there was a scare for United as the No11 motored forward and played in Henri Saivet. His snap shot was simple for Romero to save and then came a superb Anthony Martial run.

From inside his own half the forward skated through the defence and into the area. His effort rebounded off Ruffier and took Ibrahimovic by surprise, the centre-forward spooning over a left-foot attempt. As the half neared its end St-Étienne came close to equalising. Hamouma, the visitors’ stand-out performer, broke along the left and set up Kevin Monnet-Paquet but he could not beat Romero.

Mourinho’s interval message may have been to tighten up. There was a bright start when Ibrahimovic threatened in the area before Martial was booked for strong-arming Kévin Malcuit in the neck. Moments later the Swede hit the back of the net but he was offside.

Mourinho had made a first move at the break, swapping Fellaini for Jesse Lingard, who was pushed further up into a No10 role as United re-set as 4-2-3-1. Martial was arguably United’s best player and he zipped in on goal and let fly a rocket from his left boot that Ruffier did well to beat away.

The concern for United was that St-Étienne could still launch attacks and were dangerous on the break. On 62 minutes Saivet bounced Herrera off him and fed the ever-menacing Hamouma and there was relief for United when the ball was scrambled away.

Martial’s soaring confidence was summed up by a back-heel that fooled Saivet and drew a foul. Daley Blind delivered the dead ball, Pogba rose highest and he was unlucky to see the ball bounce to safety off Ruffier’s bar.

Mourinho introduced Marcus Rashford for the closing phase and it was the 19-year-old who pulled the ball back from the left for Ibrahimovic’s second.

Galtier complained about the free-kick and penalty that led to United goals. “I’m angry, frustrated about the appreciation of the game and errors made by the officials,” he said.