Robert Lewandowski took his Bundesliga tally to 10 goals in five games this season with a hat-trick as Bayern Munich thumped Eintracht Frankfurt 5-0 on Saturday, then issued a warning to the European champions' future opponents.

"I hope that we will keep this form for a very long time - it doesn't matter against who we play, we always want to show our best football, we always want to win," Lewandowski told Sky.

Lewandowski has scored nine goals in his last three league games and wrapped up his treble within an hour at the Allianz Arena.

Defending champions Bayern have scored 22 goals this term -- 10 more than league leaders RB Leipzig who stayed top with a 2-1 win over 10-man Hertha Berlin.

Bayern sit one point behind in second place.

In Munich, Leroy Sane marked his return from injury with the fourth goal during a brief cameo, before England Under-17 midfielder Jamal Musiala also came off the bench to net the fifth. 

However, Bayern's victory came at a price with Canadian left-back Alphonso Davies out for up to eight weeks with torn ankle ligaments.

Later, head coach Hansi Flick admitted Davies' injury "hurts" the European champions.

Lewandowski underlined his status as one of the world's best strikers last season by scoring a career-best 55 goals in 47 games, including 34 in the Bundesliga.

The Polish international opened the scoring on 10 minutes when he fired home after a Thomas Mueller pass.

Frankfurt goalkeeper Kevin Trapp couldn't do anything to stop Lewandowski's header from a Joshua Kimmich corner in the 26th minute.

Bayern had a penalty appeal turned down when Douglas Costa's cross clipped the hand of Frankfurt's Makoto Hasebe.

Lewandowski wrapped up the victory on the hour mark with a clinical finish from another Costa cross.

After sitting out the last two games, Sane ghosted past a defender and drove a shot into the bottom corner with 18 minutes to play.

Manuel Neuer pulled off a great save to deny Frankfurt striker Bas Dost before Musiala grabbed the final goal as the visitors suffered their first league defeat of the season.

Leipzig fight back 

Leipzig came from behind to seal a 2-1 win over Hertha, whose Colombian striker Jhon Cordoba scored in the eighth minute.

Leipzig drew level when defender Dayot Upamecano fired home from a free-kick on 11 minutes.

Berlin were reduced to 10 men after the break when substitute Deyovaisio Zeefuik was shown two yellow cards within four minutes of coming on.

Leipzig made the man advantage count when Marcel Sabitzer converted a penalty with 13 minutes left.

Hertha were lucky not to finish with nine men when another sub, Jessic Ngankam, scythed down Leipzig left-back Angelino and the referee changed his decision to a yellow card having initially shown a red.

Borussia Moenchengladbach warmed up for Tuesday's Champions League game at home to Real Madrid with a 3-2 comeback win at Mainz.

Germany midfielder Lars Stindl gave Gladbach an early lead, but the visitors were 2-1 down at half-time after French striker Jean-Philippe Mateta scored twice for Mainz.

Gladbach midfielder Jonas Hofmann converted a penalty on 76 minutes, after a shot by replacement Marcus Thuram was blocked by a Mainz hand before Matthias Ginter headed the winner as Gladbach climbed to fifth.

Union Berlin were held to a 1-1 draw at home to Freiburg as Vincenzo Grifo's first-half goal was cancelled out two minutes later by Union midfielder Robert Andrich.