Carnations are placed on the barbed wire in the former Nazi death camp of Auschwitz in Oswiecim, Poland. Reportedly Google had approved some virtual "portals" on the grounds of the concentration camp.

Google has apologised for making Nazi concentration camps part of its mobile game Ingress.

Ingress is a multiplayer augmented reality game in which people embark with their smartphones on missions to fight for control of and unlock virtual portals in a larger battle for Earth.

Players can include historic locations including monuments and markers in the game, but first they must submit those locations to be approved by Ingress.

The German weekly Die Zeit reported last week that some of these locations were located inside concentration camps such as Auschwitz, Dachau and Sachsenhausen.

"All of us here are completely appalled," Gunter Morsch , the head of the Sachsenhausen Memorial, told Die Zeit. "This is most definitely no place for video games."

Google told Die Zeit that the locations had been added to the game because they were of "significant historical value."

Ingress is made by Niantic Labs, essentially a tiny startup inside Google run by John Hanke, the brains behind Google Earth, Maps and Street View.

"After we were made aware that a number of historical markers on the grounds of former concentration camps in Germany had been added, we determined that they did not meet the spirit of our guidelines and began the process of removing them in Germany and elsewhere in Europe," Hanke said in a statement. "We apologise that this happened."

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