Berlin - Bayern Munich coach Jupp Heynckes has said his side "won't let up" as they bid to break their own record for the least amount of games needed to win the Bundesliga title.

The Bavarian giants sit 18 points clear at the top of the table - the biggest ever lead after 21 games of the 34-match season.

Bayern set the previous record under then-coach Pep Guardiola in 2013/14 when they were confirmed as champions after 27 matches.

Despite a sixth straight league title being all but assured and with a Champions League last-16 clash against Besiktas looming later this month, Heynckes insisted his team will show no mercy on their Bundesliga rivals.

"This team won't let up, regardless of what competition it is," warned the 72-year-old Heynckes on Tuesday after a 6-0 thumping of third-tier Paderborn in the German Cup quarter-finals.

Bayern have won 20 of their last 21 matches in all competitions, after a poor start to the season which saw previous coach Carlo Ancelotti sacked.

Germany defender Mats Hummels puts their red-hot form down to competition for places, with the World Cup on the players' minds.

"Motivation is a point - there is a fight for competition in each position," he said.

"At some point, national squads will be also be selected, so everyone wants to use every game to produce their best performances."

The debate about whether Bayern's vice-like grip on the league is harming the marketability of the Bundesliga is a constant theme in Germany.

Of their main rivals, only second-placed Bayer Leverkusen have enjoyed consistent results, losing just once in 19 games -- a 3-1 defeat at home by Bayern in mid-January.