Robert Lewandowski and Thomas Mueller claimed goal-scoring milestones as Bayern Munich went 16 points clear in the Bundesliga on Sunday with a 4-2 victory over Werder Bremen.

Mueller has now scored 100 Bundesliga goals in his career while Lewandowski has hit 94 German top-flight goals, making him the highest scoring foreigner in the club's history, following braces for both in a polished second-half display by Bayern's forward pair.

"Mueller has gotten his goal instincts back and Robert Lewandowski has so much class that he capitalises on those situations," enthused Bayern coach Jupp Heynkes.

Bremen took a shock first-half lead when midfielder Jerome Gondorf scored his first goal for the club.

However, Bayern went into the break level after Mueller equalised, then Lewandowski struck with the first of his two second-half headers.

Bayern defender Niklas Suele turned the ball into his own net to make it 2-2 with 15 minutes left, but Lewandowski restored the lead shortly afterwards.

He scored with a towering header to claim his 17th league goal in 18 games this season.

It leaves him as the league's top-scorer, four clear of Borussia Dortmund striker Pierre-Emerick Aubameyang.

Mueller converted a superb chip over the Bremen defence by James Rodriguez to add gloss to the final scoreline.

Bayern have won 17 from 18 games since Heynckes returned in October for his fourth stint as head coach.

The hosts were troubled when Bremen took a deserved lead on 25 minutes to stun the Munich crowd in freezing temperatures.

Werder's Germany striker Max Kruse slid a pass through the defence and midfielder Gondorf slotted through the legs of Bayern goalkeeper Sven Ulreich.

- Schalke held at home -

The ball rolled into the net, despite the efforts of Bayern right-back Joshua Kimmich to clear off the line.

Bremen grew in confidence, but the hosts drew level with a superb equaliser by Mueller just before the break.

Jerome Boateng's pin-point long pass found Mueller's chest and the Germany star slammed the ball home to make it 1-1 four minutes before the break.

Bremen's brave display meant Bayern only took the lead for the first time with an hour gone.

Rodriguez, who has recaptured the form which saw him finish top-scorer at the 2014 World Cup, fired in a cross which Lewandowski headed home.

Suele was left red-faced when the ball clipped his shoulder and rolled past Ulreich on 74 minutes.

However, Lewandowski put Bayern back ahead by leaping to smash home Mueller's cross in the 77th minute.

Lewandowski has now scored 23 goals in 27 games in all competitions this season.

Schalke climbed from sixth to third despite leaking a late equaliser to draw 1-1 at home to Hanover 96.

Schalke's new signing Marko Pjaca turned his marker in the box and fired home to put Schalke ahead on 16 minutes.

The 22-year-old striker has been loaned to Schalke until the end of the season by Juventus in his bid to win a place for Croatia at June's World Cup.

Leon Goretzka was booed by Schalke fans in Gelsenkirchen, two days after it was announced Friday that the 22-year-old will join Bayern next season.

Hanover equalised four minutes from time when striker Niclas Fuellkrug slipped his marker and fired home his fifth goal in three games and deny Schalke second place.

There is little to separate the chasing pack behind Bayern with just a point between second-placed Bayer Leverkusen and Eintracht Frankfurt in seventh place.