Rampant Celtic warmed up for their Champions League trip to Borussia Dortmund with a ninth straight win in all competitions against St Johnstone.
The defending Scottish Premiership champions thought they had led through Daizen Maeda’s first-half volley but VAR intervened over a foul.
However, Kyogo Furuhashi put the visitors in front with a typical run and finish and Paulo Bernardo completed an excellent move with a fine finish.
Kyogo headed a third in first-half added time and Callum McGregor, Maeda and substitute Adam Idah added more goals in the second period.
Brendan Rodgers’ side lead Aberdeen on goal difference at the top of the table while Saints are a point above second bottom.
The net bulged first when Maeda volleyed in from a crowded area but the officials reviewed on the grounds of Auston Trusty’s challenge on Graham Carey, who needed treatment, and found in favour of Saints.
Celtic got what they were looking for, though, when the ball bounced up off Jack Sanders near halfway and Kuhn headed through for Kyogo to beat Sinclair from the left edge of the box.
Kuhn and Kyogo were involved again in Celtic’s second, the latter laying off for Bernardo to bend into the net.
Kyogo converted Greg Taylor’s cross moments later and VAR confirmed the goal after an offside check.
A short corner involving Engels and Kuhn led to the McGregor shot from outside the box, Sinclair beaten low as the ball came through the crowd.
Bernardo crossed for Maeda’s headed score and the goal of the night came soon after.
Alex Valle played a one-two with fellow substitute Luke McCowan and backheeled for Idah to finish.
No let-up from Celtic before Dortmund trip
Celtic were much changed for last week’s 5-2 Scottish League Cup win over Falkirk and were much changed again in Perth, with injured defender Cameron Carter-Vickers still a notable absentee.
Unlike that tie with Falkirk, Celtic never found themselves behind and chasing the game, taking control early and maintaining their momentum after the disappointment of having a goal chalked off.
Kyogo, Kuhn and Trusty all threatened and once the opener came, it was a case of how many. Trusty with a shot wide and McCowan with two efforts including one off the post almost added to the rout.
At the other end, Kasper Schmeichel remains unbeaten as a Premiership goalkeeper, with Rodgers’ side matching the club’s run of six opening league wins without conceding from season 1906-07.
Greg Taylor did not return for the second half, Valle taking his place at left-back, but the Scotland international seemed to be moving freely at the full-time celebrations.
It’s Germany next for Celtic, where they will meet a Borussia Dortmund team that beat Bochum 4-2 on Friday.
Heavy loss as Saints manager hunt continues
St Johnstone showed some resistance in the early part of the game but the lack of an out ball kept the pressure coming their way.
Captain Kyle Cameron’s first-half hamstring injury added to their woes.
Aaron Essel tested Schmeichel at his near post as Saints looked for a reply at 4-0 but there would be no consolation for the Perth side, who were playing their second game under caretaker Andy Kirk following manager Craig Levein’s exit.
They face an evening encounter away to Rangers next Sunday before the international break.
What they said
St Johnstone interim manager Andy Kirk: “The disappointing thing was some of the defending. There were goals there that we could’ve avoided, absolutely. We need to defend our box better.
“We’re having a difficult period but they’ve got to stay together as a group. We’ve got to keep working hard. We’ve got to try and fix some of the problems that we’re seeing and hopefully we’ll come out on the other side of it in a better place.”
Celtic manager Brendan Rodgers: “We were excellent. From the first whistle, you saw the mentality in the team. I don’t think the players could’ve done any more.
“They’re all really good [goals] in their own right. My big thing in making this team different is the attitude in our counter pressing, the hunger. When you have that in your team, along with the talent and the organisation, it gives you a big, big chance.”
