Juve, without Cristiano Ronaldo who is still positive for coronavirus, went behind through Ousmane Dembele's deflected shot, and had Merih Demiral sent off before Lionel Messi's penalty made it 2-0.

United put their German opponents to the sword in Group H as Mason Greenwood and Anthony Martial both scored and Marcus Rashford grabbed a hat-trick from the bench.

Paris Saint-Germain won 2-0 at Istanbul Basaksehir despite losing Neymar to injury while Chelsea defeated Krasnodar 4-0 in Russia.

Barcelona started the better in Turin and needed only 14 minutes to open the scoring. Dembele let fly from outside the area, and his shot looped over Wojciech Szczesny after hitting Federico Chiesa.

Spain international Morata then had the ball in the back of the net three times, twice in the first-half and once after the break, but he was in an offside position on each occasion.

"We knew it would have been a difficult game against a team who can play football and are further than us in their own path," said Juventus coach Andrea Pirlo.

"They have players who are used to playing this kind of game while we had many in their second Champions League appearance only."

Ronald Koeman's side were in the ascendancy but did not double their lead till injury-time. Messi netted from the spot just six minutes after Demiral received a second yellow card for a late foul on Miralem Pjanic.

"The best response we could give to the turmoil at the club is a display like this. Everybody has been talking a lot but the team simply want to win games," said Barcelona midfielder Sergio Roberto, a day after president Josep Bartomeu resigned.

Manchester United were far too good for last season's semi-finalists Leipzig, who failed to secure a first German win at Old Trafford since Bayern Munich in 2001.

Paul Pogba's pass was superbly finished by Greenwood midway through the first half and keeper David de Gea preserved the lead into the final half-hour.

Rashford's introduction saw the game burst into life. He raced onto Bruno Fernandes' pass to bag his first before drilling his second past Peter Gulacsi.

He then hammered in from inside the penalty area for the first senior hat-trick of his career after Martial's penalty had made it 4-0.

"Marcus was fantastic," said United manager Ole Gunnar Solskjaer. "You hope you can make an impact off the bench, and when you've got players like that in reserve it's great for us."

PSG picked up all three points at Basaksehir to move level with Leipzig in the group.

Neymar was forced off just 26 minutes into the game with a hamstring issue having attempted to carry on with heavy strapping on his thigh, but to no avail.

Moise Kean made sure the beaten finalists from last season didn't miss their talisman too much - he claimed his first two goals in the competition, both coming via assists from Kylian Mbappe.

Chelsea top Group E despite a missed penalty from Jorginho early on at Krasnodar, after goals from Callum Hudson-Odoi, Timo Werner (penalty), Hakim Ziyech and Christian Pulisic.

Ferencvaros drew 2-2 with 10-man Dynamo Kyiv, Club Brugge drew 1-1 with Lazio, Dortmund defeated Zenit 2-0 while Sevilla beat Rennes 1-0 to complete Wednesday's action.

Australian Associated Press