Barcelona's lethal MSN -- Lionel Messi, Luis Suarez and Neymar -- dissected Celtic 7-0 while a deluge washed out Pep Guardiola's eagerly awaited first Champions League game in charge of Manchester City on Tuesday.

There was no rain but there was a flood of goals at the Camp Nou, where a sparkling Messi hat-trick with four assists and a goal from Neymar, Andres Iniesta and a Suarez brace humiliated Celtic.

"There can be no embarrassment because they do that to better teams than ourselves," said Celtic boss Brendan Rodgers.

"They are special players. It is a front three that can occupy as many players as you want."

Suarez, reunited with Messi and Neymar for the first time this season, told TV3: "It has been many games since we have been able to enjoy being on the pitch together and today we did."

Celtic will have to shrug off this worst ever European defeat as their next Group C outing is at home to City.

After the weekend derby defeat of Manchester United, City had Borussia Moenchengladbach firmly in their sights but the fixture was called off just 20 minutes before kick-off with the Etihad Stadium hit by heavy rain.

The match will now be played on Wednesday at 1845GMT.

The first goal of the 2016/2017 Champions League group stages came after a mere 42 seconds from the head of Paris Saint Germain striker Edinson Cavani at the Parc des Princes against Arsenal.

The strike was PSG's quickest in the Champions League, but the French champions, and Cavani in particular, were guilty of failing to convert a succession of golden opportunities.

Barcelona decimated Celtic 7-0. Reuters

The worst possible start for Arsenal hinted at a potential lopsided affair but the Gunners got out of jail with Alexis Sanchez's leveller inside the final quarter of an hour.

Arsenal's night got better with news that Group A's other game between Basel and Ludogorets also ended 1-1.

Guardiola's old side Bayern Munich, under new boss Carlo Ancelotti, ran riot over Russian side Rostov 5-0.

Joshua Kimmich grabbed a second-half double, with Robert Lewandowski scoring from the penalty spot, birthday boy Thomas Mueller and Spanish defender Juan Bernat giving Bayern early custody of Group D.

But only on goal difference as Atletico Madrid won 1-0 at PSV Eindhoven, Saul Niguez doing the damage with a sizzling scissor-style volley just before the break.

Barca meanwhile could face fresh sanctions from UEFA after thousands of separatist Catalan flags were again flown at the Camp Nou.

The Spanish champions were fined 150,000 euros ($170,000) by UEFA because of the flags during last season's competition.

Feature image source: Twitter