Merkel noted her visit came amid rising anti-Semitism and historical revisionism.

She says Germany remains committed to remembering the crimes it committed against Jews, Poles, Roma and Sinti, homosexuals and others.

Speaking to a gathering including former Auschwitz inmates on Friday, she said she felt "deep shame in the face of the barbaric crimes committed by Germans here".

"Nothing can bring back the people who were murdered here. Nothing can reverse the unprecedented crimes committed here. These crimes are and will remain part of German history and this history must be told over and over again," she said.

She called such responsibility a key element in German national identity today.

Merkel also brought a donation of 60 million euros ($A97.3 million).

The money will go to a fund to conserve the physical remnants of the site - the barracks, watchtowers and personal items like shoes and suitcases of those killed.

The objects endure as evidence of German atrocities and as one of the world's most recognisable symbols of humanity's capacity for evil but are also deteriorating under the strain of time and mass tourism.

Accompanied by Polish Prime Minister Mateusz Morawiecki, Merkel began by seeing a crematorium and walking under the gate with the notorious words "Arbeit Macht Frei".

The phrase means "work will set you free" but the truth was inmates were subjected to either immediate execution, painful scientific experiments or forced labour.

Merkel and Morawiecki went next to the site of executions, where they bowed their heads before two wreaths bearing their nations' colours.

The stay lasting several hours also included a visit to the conservation laboratory, where old leather shoes were laid out, and a laying of candles at Birkenau, the part of the vast complex where Jews were subjected to mass murder in gas chambers.

Australian Associated Press