Germany has around 2,600 such markets, filled with sparkling Christmas trees and wooden stalls serving candied nuts, sausages, mulled wine and handicrafts.
Reports said the package contained nails and some kind of powder.
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The Reuters agency cited the Potsdamer Neueste Nachrichten newspaper, which described the package as 40 cm (15.75 inches) by 50 cm large.
POLICE have evacuated a Christmas market in Germany after a bomb was delivered to nearby pharmacy, nearly a year after a deadly terrorist attack on a similar target.
The package was dropped off by a messenger service in the afternoon at a chemist in the Brandenburg state capital just as crowds were gathering at the nearby Christmas market.
Translated into English, the post says: "The suspicion of an IED has been confirmed". Police were called and the area was evacuated.
Around half an hour later they sent a second message saying their officers had defused the device.