BERLIN, Sept. 21 (Xinhua) -- Defending champions Bayern Munich maintained their unbeaten start to the season after moving 4-0 past ten-men Cologne on Robert Lewandowski's brace at the 5th round in Bundesliga on Saturday.

The German record champions did not need much time to warm up as Lewandowski broke the deadlock after beating Cologne goalkeeper Timo Horn with a deflected shot from inside the box with only three minutes into the game.

Bayern retracted with the narrow lead behind but still they came to chances as Philippe Coutinho rattled the woodwork with a free kick before Ivan Perisic pulled wide at tha half hour mark.

Cologne showed vital signs before the half time as Jhon Cordoba missed twice from promising positions.

After the restart, Lewandowski again wasted no time to score as he headed home Joshua Kimmich's corner to score his ninth goal in his fifth Bundesliga game of the season.

Bayern pressed relentless and tripled the lead with the helping hand of Cologne's Kingsley Ehizibue, who felled Coutinho inside the box to see a straight red card. Coutinho stepped up and made no mistake to score his maiden goal for the Bavarians from the penalty spot.

The visitors were unable to hold the pace whereas Bayern were not done with the scoring as Coutinho set up for Perisic, whose left footed effort into the bottom right corner made it 4-0 on the scoreboards.

With the result, Bayern Munich climb on the top spot for the moment meanwhile Cologne slipped to the 16th place after suffering their fourth loss from five games.

Elsewhere, Bayer Leverkusen returned to winning ways after three winless games as goals from Lucas Alario and Kevin Volland downed ten-men Union Berlin 2-0.

Hertha Berlin secured their first win of the campaign after overcoming newly promoted Paderborn 2-1 and Freiburg squandered the chance to climb atop the standings after sharing the spoils with Augsburg following a 1-1 draw.