BERLIN—A Serbian man was arrested in southern Germany on Tuesday after an altercation on board a Serbia-bound bus and an ensuing standoff led to the closure of a section of highway in Bavaria, police said. The incident started with a fight involving several passengers that left two people slightly injured, police said. They added in a statement that the fight escalated into a “threat situation,” and the bus stopped on the A9 highway between Hilpoltstein and Greding, south of Nuremberg. The highway section was closed in both directions. The passengers then left the Serbian bus. Three drivers and a man who apparently had a weapon remained on board. Police officers tried to contact the apparently armed man. He was arrested without resisting after they managed to reach one of the drivers by cellphone and all three drivers left the bus. Investigators didn’t immediately find any weapons either on the 30-year-old …