It was Merkel's third visit to visit troops and, as always, it wasn't announced in advance for security reasons, Deutsche Welle reported.
Merkel was accompanied by German Defense Minister Karl-Theodor zu Guttenberg and military Chief of Staff Volker Wieker, the German broadcaster said.
Germany has more than 4,800 troops serving primarily in two camps in northern Afghanistan. Foreign Minister Guido Westerwelle said in a parliamentary speech Thursday Germany would begin making troop reductions in Afghanistan late next year, CNN reported.
Just prior to Merkel's arrival, military officials said an unidentified 21-year-old German soldier had died in surgery for injuries unrelated to combat.
Germany has lost 45 troops in the Afghanistan mission, 27 of whom died in combat, the report said.