The club confirmed Lahm's broken ankle via Twitter following an examination by doctors.
Fans had already feared the worst: immediately after the incident the player was seen on the ground screaming in pain, shouting "S***!" repeatedly and grabbing his right ankle.
He was then taken from the training pitch on the back of a buggy.
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Broken ankle
Bayern tweet
Lahm was one of Germany's key players during the World Cup victory this summer, but he has since retired from international duty.
And his absence has been blamed by many for the Mannschaft's poor showings since the tournament in Brazil, with Joachim Loew's team now facing an uphill battle just to qualify for Euro 2016.
The 31-year-old's form, by contrast, has been exemplary, with the defender-cum-midfielder a key man in Bayern's near-perfect start to the season.
Yet the German champions' start to the season has come at a high price: Lahm is just the latest high-profile player to be injured, as this extraordinary team line-up of their currently-sidelined stars shows:
Bayern's injured XI
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