BERLIN: Bayern Munich's Robert Lewandowski and Thomas Mueller scored two goals each as the German champions crushed hosts Arminia Bielefeld 4-1 in the Bundesliga on Saturday to move within a point of top spot.

Mueller scored either side of Lewandowski's double, with the Polish striker taking his season's tally to seven league goals from four games, as Bayern moved to nine points, level with third-placed Borussia Dortmund and one behind leaders RB Leipzig, who won 2-0 at Augsburg.

"The first half was very near to what we see as perfect football," Bayern coach Hansi Flick said of his team's strong first half. "But at times we have to be more clever to save energy."

Bayern, who also twice hit the woodwork, have a busy schedule, having played in the German Cup and league this week and next facing Atletico Madrid in the Champions League on Wednesday.

"We are currently missing some training sessions (due to the shortened summer break). Borussia Dortmund had six weeks to prepare, we had only a week of team training."

Mueller grabbed an eighth minute lead with a bit of luck after his first effort was saved but the ball bounced back into his path, while Lewandowski was left with far too much space to score with a well-placed shot in the 26th.

Arminia goalkeeper Stefan Ortega kept the scoreline respectable in the first half with several spectacular stops, including a sensational one-handed save from Lewandowski's close-range header.

But the home keeper was beaten again with the last kick of the first half, a deflected shot from Lewandowski after good work from Mueller.

Bayern, who had to use changing rooms in a nearby school ahead of the game due to strict COVID-19 regulations, scored again six minutes after the restart when Lewandowski crossed and Mueller volleyed in from close range.

Arminia's Japan international Ritsu Doan was rewarded for a fine performance with a goal in the 58th before Bayern were left with 10 men following the dismissal of Corentin Tolisso for a last-man foul.