Harry Kane scored from the penalty spot as Bayern Munich piled more misery on struggling Manchester United with a 4-3 home win in the Champions League on Wednesday.

United travelled to Germany after a poor run of form and amid a raft of off-field issues and were offered little respite by a Bayern side who have now won their past 20 Champions League opening matches.

It was a fourth defeat in just six matches for Erik ten Hag's floundering United in all competitions this season as they failed to bounce back from last weekend's embarrassing 3-1 home loss to Brighton in the Premier League.

Bayern took control when visiting goalkeeper Andre Onana let Leroy Sane's weak shot roll into the net in the 28th minute before Serge Gnabry swept home a second.

Rasmus Hojlund pulled one back before Kane drilled in a penalty early in the second half.

Casemiro's late effort briefly gave United hope of an unlikely comeback against the run of play, but Bayern substitute Mathys Tel smashed home a fourth for the hosts in added time.

Brazilian Casemiro nodded in another consolation goal for United from the last attack of the match.

Six-time European champions Bayern moved top of the early Group A table after Wednesday's earlier 2-2 draw between Galatasaray and FC Copenhagen in Istanbul.

Coming into the match, Ten Hag said the challenges would teach his side to "focus on the process".

Early on, they controlled possession and forced Bayern onto the back foot.

Bayern would strike first, however, thanks to some clever work from Kane and Sane -- and a poor mistake from Onana.

Sane evaded his marker and threaded a ball to Kane, who guided the ball back into the path of the former Manchester City winger.

Sane slid the ball goalwards and Onana made a meal of the save and allowed it to trickle into the net.

Bayern celebrated as Onana lay forlorn on the Allianz Arena turf.

If Bayern's first was a mix of team understanding and good fortune, the second came about mainly thanks to the individual brilliance of Jamal Musiala.

The England-raised midfielder, 20, collected the ball near the halfway line and dribbled goalwards, fending off the attention of several United defenders before squaring for Gnabry.

The former Arsenal forward slammed the ball into the net to leave United 2-0 down and reeling after a solid if unspectacular start.

The visitors did give their travelling fans hope just after half-time when United collected a poor back-pass from Musiala, Marcus Rashford finding summer signing Hojlund whose deflected shot evaded goalkeeper Sven Ulreich.

United's hope was short-lived however, a VAR review finding a handball in the box from Christian Eriksen.

United complained about the call, with Eriksen clearly trying to withdraw his arm while having little time to react, but Kane stepped up and converted the spot-kick, his fifth goal in five starts for Bayern.

United rallied late on, Casemiro scoring either side of a Mathys Tel goal, but Bayern were never in serious danger of relinquishing the three points.