It was his 101st goal in European club football's most prestigious competition. Numbers 102 and 103 followed after the France international Ousmane Dembélé had doubled the advantage 15 minutes from time.
Barcelona will next travel to London to play Tottenham Hotspur who allowed Inter Milan to score two late goals for a 2-1 victory at the San Siro.
Christian Eriksen gave the Spurs the lead early in the second half but with an impressive away win looming, Mauro Icardi thrashed home an equaliser from 20 metres and Matias Vecino snatched the winner in stoppage time.
"This is exactly what the fans want to see," said Inter coach Luciano Spalletti.
"Icardi scored a magnificent goal. The team had a great game and really went for it in the end."
The win leaves Inter second in Group B behind Barcelona on goal difference.