A man holds flowers during a ceremony marking the 71st anniversary of Mauthausen Concentration Camp's liberation in the state of Upper Austria, Austria, May 15, 2016. More than 6,000 people gathered to commemorate the 71st anniversary of the liberation of the Mauthausen concentration camp on Sunday. (Xinhua/Qian Yi)

Polish girls attend a ceremony marking the 71st anniversary of Mauthausen Concentration Camp's liberation in the state of Upper Austria, Austria, May 15, 2016. More than 6,000 people gathered to commemorate the 71st anniversary of the liberation of the Mauthausen concentration camp on Sunday. (Xinhua/Qian Yi)

A person stands in front of a monument at Mauthausen Concentration Camp in the state of Upper Austria, Austria, May 15, 2016. More than 6,000 people gathered to commemorate the 71st anniversary of the liberation of the Mauthausen concentration camp on Sunday. (Xinhua/Qian Yi)

Elders attend a ceremony marking the 71st anniversary of Mauthausen Concentration Camp's liberation in the state of Upper Austria, Austria, May 15, 2016. More than 6,000 people gathered to commemorate the 71st anniversary of the liberation of the Mauthausen concentration camp on Sunday. (Xinhua/Qian Yi)

Representatives from Chinese Embassy pay tribute to those killed during a ceremony marking the 71st anniversary of Mauthausen Concentration Camp's liberation in the state of Upper Austria, Austria, May 15, 2016. More than 6,000 people gathered to commemorate the 71st anniversary of the liberation of the Mauthausen concentration camp on Sunday. (Xinhua/Qian Yi)

Elders pay tribute to those killed during a ceremony marking the 71st anniversary of Mauthausen Concentration Camp's liberation in the state of Upper Austria, Austria, May 15, 2016. More than 6,000 people gathered to commemorate the 71st anniversary of the liberation of the Mauthausen concentration camp on Sunday. (Xinhua/Qian Yi)

People attend a ceremony marking the 71st anniversary of Mauthausen Concentration Camp's liberation in the state of Upper Austria, Austria, May 15, 2016. More than 6,000 people gathered to commemorate the 71st anniversary of the liberation of the Mauthausen concentration camp on Sunday. (Xinhua/Qian Yi)