New York - Mourners gathered in New York on Sunday to bid farewell to Elie Wiesel, the Holocaust survivor and Nobel peace laureate hailed for his life's work of keeping alive the memory of Jews slaughtered during WWII.Wiesel, who died in New York on Saturday at age 87, was honoured at private services at a synagogue on the Upper East Side neighbourhood of Manhattan, as tributes poured in from around the world.His wife Marion, in a wheelchair, was among those who arrived in a stream of black cars. The service began at about 11:00 (15:00 GMT). "It's a great loss for Jewish people. It's a great loss for mankind. He was a unique individual and we will miss him dearly," Ronald Lauder, the president of the World Jewish Congress, told reporters outside the synagogue.The Romanian-born Wiesel, a US citizen once known as "the world's leading spokesman on the Holocaust", was perhaps best known for his memoir Night detailing his experiences in Nazi death camps.He won the Nobel Peace Prize in 1986, when he was described as having "made it his life's work to bear witness to the genocide committed by the Nazis during World War II."In his Nobel acceptance speech, he said the award "both frightens and pleases me"."It frightens me because I wonder: Do I have the right to represent the multitudes who have perished? Do I have the right to accept this great honour on their behalf?"I do not. That would be presumptuous. No one may speak for the dead, no one may interpret their mutilated dreams and visions."'Exemplar of humanity'Tributes poured in for Wiesel from world leaders including Israeli Prime Minister Benjamin Netanyahu, who reportedly tried to convince the Holocaust survivor to run for president in 2014."Elie, a master of words, expressed in his unique personality and fascinating books the victory of human spirit over cruelty and evil," Netanyahu said in a statement. "In the darkness of the Holocaust, in which six million of our brothers and sisters perished, Elie Wiesel was a beacon of light and an exemplar of humanity that believes in man's good."US President Barack Obama hailed Wiesel as "one of the great moral voices of our time, and in many ways, the conscience of the world".At the US Holocaust Memorial Museum, which Wiesel helped to create, the facility's chair, Tom Bernstein, said the world "feels incomplete" after Wiesel's death."He was a transformative figure who exemplified the very ideals that the Museum encourages all to aspire to - that memory calls us to action. We all bear the tremendous responsibility to carry on his legacy," he said.'Living memorial'Eliezer Wiesel was born on September 30, 1928 and grew up in a small town in Romania.His parents raised him and his three sisters in a Jewish community, until they were all detained during the Holocaust when he was a teenager.His mother and younger sister were killed in the gas chamber at Auschwitz, according to his biography. His father died of dysentery and starvation at Buchenwald, where Wiesel was freed by US soldiers at the age of 17.He was reunited with his two older sisters in France, and eventually studied at the Sorbonne in Paris.Wiesel travelled back to Auschwitz in 2006 with US talk show host Oprah Winfrey. He also accompanied Obama and German Chancellor Angela Merkel on a tour of the Buchenwald camp."After we walked together among the barbed wire and guard towers of Buchenwald... Elie spoke words I've never forgotten - 'Memory has become a sacred duty of all people of goodwill'," Obama said on Saturday."Elie was not just the world's most prominent Holocaust survivor, he was a living memorial," he added."His life, and the power of his example, urges us to be better."Merkel said that "a voice of morality and humanity has been silenced" with the death of Wiesel, whom she praised as a "big-hearted reconciler.""Elie Wiesel has offered the hand of friendship to us Germans and worked tirelessly with us to make a better world."Writer, scholar, activist Wiesel's internationally acclaimed Night was published in 1956 and has been translated into more than 30 languages. It was later expanded into a trilogy with Dawn and Day.While Wiesel's focus was the Holocaust and the plight of the Jewish people, he was also a rights activist and a professor of Judaic studies and the humanities.Soon after he won the Nobel prize, Wiesel and his wife founded The Elie Wiesel Foundation for Humanity with a mission to "combat indifference, intolerance and injustice through international dialogue and youth-focused programmes.""The world has lost one of its most important witnesses - and one of its most eloquent advocates of tolerance and peace," UN Secretary General Ban Ki-moon said.