Munich's scorer Robert Lewandowski and his teammate Thomas Mueller celebrate the opening goal during the German Bundesliga soccer match between FSV Mainz 05 and FC Bayern Munich in Mainz, Germany, Feb 1, 2020. (TORSTEN SILZ / DPA VIA AP)

BERLIN - Bayern Munich jumped atop the table for the moment after beating Mainz 3-1 on three first-half goals, and Erling Haaland's brace helped Borussia Dortmund to whitewash newly promoted Union Berlin 5-0 at the 20th round in Bundesliga on Saturday.

Erling Haaland became the first player in history to net seven goals in his first three Bundesliga outings

The German record champions needed a powerful first half to beat Mainz as goals from Robert Lewandowski, Thomas Muller and Thiago Alcantara were enough to snatch all three points on the road.

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Bayern secured a bright start and needed only eight minutes to break the deadlock as Benjamin Pavard's pinpoint cross into the box allowed Lewandowski to mark his 22nd goal of the season by header.

The Bundesliga top striker remained in the thick as he ran goalwards before he was brought down by goalkeeper Robin Zentner at the edge of the box. Mulller reacted as the quickest and tapped home the loose ball to double the lead in the 14th minute.

Mainz tried to respond but was unable to hold the pace especially when Thiago danced through Mainz' defence before finishing off his solo run with a hammer past Zentner at the 26th minute.

The hosts sparked to life just before the break when Jeremiah St. Juste headed home a corner to reduce the arrears out of the blue.

After the restart, harmless Mainz were unrecognisable as their goal gave them confidence to keep  the "Bavarians" on the distance until the 75th minute.

Mainz tested Bayern goalkeeper Manuel Neuer several times but Bayern's sixth straight victory was never in jeopardy.

With the result, Bayern Munich opened up a two-point advantage atop the standings for now while Mainz remain on the 15th place.

Dortmund's scorer Erling Haaland celebrates after he scored his second goal during the German Bundesliga soccer match between Borussia Dortmund and Union Berlin in Dortmund, Germany, Feb 1, 2020. (MARTIN MEISSNER / AP)

Borussia Dortmund closed the gap to the top spot after sweeping newly promoted Union Berlin 5-0 off the pitch.

Union grabbed the better start into the clash but Marius Bluter missed a ball from very close range with just four minutes played.

From then on, the "BVB" immediately assumed control and pressed the visitors on the back foot. It was thus just a matter of time before the hosts opened the scoring, as Dortmund forced a turnover at the edge of the box before Jadon Sancho slotted home from tight angle in the 14th minute.

Dortmund gained momentum and needed only four more minutes to double their advantage as Julian Brandt found prolific new arrival Haaland, who tapped home from central position inside the box.

The hosts dominated the proceedings on the pitch but had to wait after the half time to extend their lead, as Rafal Gikiewicz felled Haaland inside the box. Marco Reus stepped up and made no mistake to triple the lead in the 68th minute.

The visitors resistance was broken moments later when Axel Witsel completed a fast break from close range into the roof of the net.

Haaland wasn't done with the scoring and became the first player in history to net seven goals in his first three Bundesliga outings.

With the 11st win of the season, Dortmund move on the third place meanwhile Union Berlin slipped to the 12th position in the table.

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Elsewhere, last placed Fortuna Dusseldorf dropped vital points as Eintracht Frankfurt's Timothy Chandler scored a late 1-1 equalizer.

Augsburg increased Werder Bremen's relegation worries after coming from behind to seal a 2-1 win on Florian Niederlechner's and Ruben Vargas' goals, and Hoffenheim turned the tides to edge Bayern Leverkusen 2-1.