Police close the streets around a Christmas market after a suspicious object was found in Potsdam, eastern Germany. Picture: Julian Staehle/dpa via AP

Berlin - Experts on Friday defused an explosive device found near an outdoor Christmas market in the German city of Potsdam near Berlin, local police said on Twitter.

Germany is on high alert for potential militant attacks nearly a year after a Tunisian Islamist hijacked a truck, killed its driver, and then rammed the vehicle into a Christmas market in central Berlin, killing 11 people there.

In Potsdam, police cordoned off the area including the market after being alerted about a suspicious object that had been delivered to a pharmacy.

"The suspicion of an (improvised explosive device) has been confirmed," police said on Twitter. No additional details were immediately available. "It is still being investigated what exactly the suspicious object is," they said in another Tweet.

The Potsdamer Neueste Nachrichten newspaper said the pharmacy alerted police after receiving a package measuring 40 cm (16 inches) by 50 cm (20 inches) that contained suspicious wires and electronics.

The Potsdam newspaper said police were alerted around 2:30 p.m. (1330 GMT). Police announced on Twitter about three hours later that the object had been defused.

Police close the streets around a Christmas market after a suspicious object was found in Potsdam, eastern Germany. Picture: Julian Staehle/dpa via AP

Christmas markets opened across Germany on Monday at the start of the holiday season, fortified with security staff and concrete barriers to protect shoppers.

Germany has around 2,600 such markets, filled with sparkling Christmas trees and wooden stalls serving candied nuts, sausages, mulled wine and handicrafts.

Interior Minister Thomas de Maiziere said this week Germany had increased information-sharing between federal and state officials and taken other steps to increase security after a series of missteps in the Berlin case.

A Ministry spokesman said this week the risk of an attack in Europe and Germany is "continuously high".