Bayern Munich forward Serge Gnabry will undergo an operation Wednesday for a fractured lower arm, an injury that will set him out for "several weeks", coach Thomas Tuchel said.

Gnabry suffered the injury during a German Cup game late Tuesday against third division side Preussen Muenster.

"It's bitter. He is an important player and a super character," said Tuchel, adding that he will "miss several weeks".

Gnabry will have to sit out a number of Bayern's upcoming fixtures, including a Bundesliga away match with Leipzig on Saturday as well as a Champions League group game away at Copenhagen on Tuesday.

His participation will also be in doubt when new Germany coach Julian Nagelsmann makes his debut during an October trip to the United States for friendlies with the US and Mexico.

Gnabry was substituted after 11 minutes following a collision with Muenster goalkeeper Johannes Schenk.

An X-ray subsequently confirmed the fracture.