Lionel Messi notched a hat-trick as Barcelona bounced back from their shock weekend defeat to Alaves by hammering Celtic 7-0 in their Champions League opener on Tuesday night.
Luis Enrique's men were stunned 2-1 by newly-promoted Alaves at the Nou Camp in LaLiga on Saturday, but made amends by recording their biggest Champions League victory.
Aside from Messi's sixth career treble in the competition, Neymar and Andres Iniesta were also on the scoresheet with fine second-half strikes before Luis Suarez wrapped things with two more goals late on.
It might have been a different story had Moussa Dembele - hat-trick hero in Celtic's 5-1 derby mauling of Rangers at the weekend - not seen his 24th-minute penalty saved by Marc-Andre ter Stegen when it was 1-0, but the Scottish champions were convincingly beaten in the end.
The record victory sees Barca take early control of Group C, with the other match in the pool between Manchester City and Borussia Monchengladbach at the Etihad Stadium being postponed due to adverse weather conditions.
Bayern Munich were similarly one-sided winners in Group D as they brushed aside Rostov 5-0 at home.
Robert Lewandowski, from the penalty spot, and Thomas Muller put Bayern in the ascendency before the break and a second-half brace from Joshua Kimmich and a late Juan Bernat effort completed the rout.
Bayern's triumph puts them top of a tough-looking Group D, ahead of last season's runners-up Atletico Madrid, who were 1-0 victors at PSV Eindhoven.
Saul Niguez's acrobatic effort in the 43rd minute settled the contest in favour of Diego Simeone's men, with PSV missing a controversially-awarded penalty moments later as Jan Oblak superbly kept out Andres Guardado's spot-kick.
Paris St Germain had to settle for a point in their Group A opener as Arsenal fought back for a 1-1 draw at the Parc des Princes.
Edinson Cavani gave the French powerhouses a flying start with the opening goal after 41 seconds, but Alexis Sanchez drilled home an equaliser 12 minutes from time. PSG midfielder Marco Verratti and Arsenal striker Olivier Giroud were both dismissed in stoppage time for second cautions.
It also finished 1-1 in Basle, where the hosts salvaged a point with a late leveller against Ludogorets. Cafu's goal on the counter-attack gave the Bulgarian side the lead on the stroke of half-time, but Renato Steffen levelled for Basle 10 minutes from the end.
Napoli are the early front-runners in Group B after Arkadiusz Milik's brace fired them to a 2-1 a comeback victory at 10-man Dynamo Kiev.
Denys Garmash gave Dynamo a 26th-minute lead, but their hopes of earning a point after Milik's first-half brace were all but ended when midfielder Serhiy Sydorchuk was sent off in the 68th minute.
The match between Benfica and Besiktas in Portugal finished 1-1 as Anderson Talisca's brilliant stoppage-time free-kick for the Turkish side cancelled out Franco Cervi's early opener.