ASHKELON, Israel (Reuters) - For 80-year-old David Ariel, a survivor of the Nazi Holocaust, parting with cherished letters from his mother, killed at Auschwitz death camp, was a painful but necessary duty.
Ariel and thousands of other elderly Israeli survivors answered a call by Yad Vashem, Israel's national memorial to the six million Jews killed in the genocide, to hand in Holocaust-era keepsakes to preserve their memory for future generations.
Ariel's contribution to Yad Vashem's "Fragments of Memory" campaign consisted of the few letters his mother Zelma had written to a cousin before she was deported and killed at Auschwitz during World War Two.
He recovered them after immigrating to Israel once the war was over -- a treasured memento for a man who had lost his entire family to the Nazis.
"I felt like I was separating from her all over again when I handed them in, even though I knew I didn't have the proper conditions to preserve them and they were starting to yellow and tatter," he said.
Yad Vashem chairman Avner Shalev said the drive to collect fading memorabilia, including letters, photographs, toys and articles of clothing, before survivors died was "a kind of race against time so that they will be remembered."
The Holocaust narrative remains a focal point for Israel, where some 200,000 survivors live. The Jewish state holds its annual Holocaust remembrance day on Monday.
Recent attempts to deny the Holocaust, particularly by Israel's arch-enemy Iran, have refocused Israeli efforts to collect survivors' testimonies and relics.
"Imagine if we had six million testimonies, it would stand for ever against all the Holocaust deniers," Shalev said. "Perhaps this is thinking virtually, but practically any new testimony or artefact adds something to this process."
Ariel, born in Czechoslovkia and a retired lieutenant colonel in the Israeli military, wept as he described his wartime ordeals.
Taken at the age of 13 to Auschwitz, in Poland, he spent a week in the death camp before being sent to Mauthausen concentration camp in Austria, where he survived for months on food scraps as a slave labourer.
"People all around me were dying like flies. I don't know how I survived," said Ariel, whose father, a brother and a sister also perished at Auschwitz.
(Corrects in paragraphs 3,4 to clarify letters' addressee)
Editing by Mark Trevelyan