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Hansi Flick's side, which was wearing Black Lives Matter armbands, looked rusty during the opening exchanges on Sunday (AEST) yet rallied to overpower its host and go 10 points clear of Borussia Dortmund at the top of the table.

It all began so well for Leverkusen, which opened the scoring early on through Lucas Alario, but it capitulated and conceded three goals in less than 20 minutes, Kingsley Coman, Leon Goretzka and Serge Gnabry all punishing the home side.

Lewandowski added a fine header to set a new personal best of 44 goals in a single season, turning in a cross from Muller, who equalled the Bundesliga assists record for a solitary campaign.

Despite not being able to call upon Kai Havertz, missing with a muscular issue, Leverkusen began positively and deserved the lead nine minutes in, Alario prodding past Manuel Neuer after being released by Julian Baumgartlinger.

But its confidence soon vanished and Bayern duly restored parity just before the half-hour mark, Coman slotting past Lukas Hradecky after Goretzka robbed Moussa Diaby to set up his team-mate.

Leverkusen then fell apart late in the half. Goretzka rounded off a well-worked move with a left-footed effort than squeezed under Hradecky's hand, while Gnabry lobbed the goalkeeper to make it 3-1 after a punt up the pitch by Joshua Kimmich.

Peter Bosz took the drastic step of making three changes at half-time, and while chances became slightly harder to come by for Flick's team, Leverkusen did not improve a great deal going forward.

Bayern looked the more threatening and eventually got a fourth just past the hour, with Lewandowski belatedly getting in on the act with an emphatic header from Muller's pinpoint cross.

Florian Wirtz, who was introduced at the break, opened his Leverkusen account in style with a curling effort late on to become the Bundesliga's youngest ever scorer at 17 years and 43 days, but it was a mere consolation for the hosts.

Bayern will return to Allianz Arena for a DFB-Pokal semi-final against Eintracht Frankfurt on Thursday (AEST), then it hosts Borussia Monchengladbach in the Bundesliga three days later.

Leverkusen is also in cup action in midweek, against fourth-tier Saarbrucken on Wednesday (AEST), before heading to Schalke for a weekend Bundesliga clash, where it will hope to bounce back in the fight for a UEFA Champions League spot.