Thomas Mueller scored a hat trick as Bayern Munich opened its German Cup defence with a 5-0 win over fourth-tier side BSV Rehden on Monday.

"Such a game is always dangerous," Bayern coach Pep Guardiola said. "So we're happy."

Xherdan Shaqiri opened the scoring in the 18th, deflecting in Arjen Robben's shot from close range after the Rehden defense failed to clear the ball.

Mueller was unmarked when he scored just before halftime with a header from Rafinha's cross.

Rehden goalkeeper Milos Mandic denied Mario Mandzukic with an acrobatic save early in the second half, and Mueller hit the crossbar from the resultant corner.

However, the Bayern attacker dusted himself off to make it 3-0 from the penalty spot after he was brought down in the area in the 58th, and he completed his hat trick in with a header in the 64th.

Mueller was still furious with himself for missing another chance late on, before Robben wrapped up the scoring two minutes from time.

"We're not perfect yet," Robben said. "We're not at 100 percent but that's normal. We're ready for the Bundesliga regardless. We'll be there on Friday."

Earlier Monday, Klaas-Jan Huntelaar scored one goal and set up another for Schalke to defeat fifth-tier FC Noettingen 2-0 to advance to the second round.

Huntelaar struck in the 30th minute but the visitors were made to wait until the fourth minute of stoppage time before the Dutchman could set up offseason signing Leon Goretzka to secure the result.

"They played well in the first half, hit the crossbar twice," Huntelaar said. "We were bad, you have to be honest."

Second-division side Paderborn defeated third-tier MSV Duisburg 3-2, and another second-division side, Union Berlin, won 2-1 at third-division Jahn Regensburg.