A Hungarian man has been acquitted by a Budapest court of committing war crimes during a 1942 raid.
Ex-police captain Sandor Kepiro, 97, was found not guilty of ordering the rounding up and execution of more than 30 Jews and Serbs in Serbia in 1942.
The prosecution had demanded at least a prison sentence for Mr Kepiro, but he insisted he had not killed.
The Simon Wiesenthal Center, which listed him as its most wanted Nazi, said the verdict was "outrageous".
The group's chairman, Efraim Zuroff, said they would appeal against it.
Many of the dozens of people attending the court session cheered and clapped after Judge Bela Varga read out the verdict of the three-judge tribunal, AP news agency reported.
The reasoning behind the court's verdict is being read out over two days - Monday and Tuesday - in light of the frailty of the defendant.
More than 1,200 Jewish, Serb and Roma civilians were murdered over three days by Hungarian forces in a notorious massacre in the city of Novi Sad in 1942.
Prosecutors said Mr Kepiro was directly responsible for the deaths of 36 Jews and Serbs - including 30 who were put on a lorry on the defendant's orders and taken away and shot.
He was convicted of involvement in the killings in Hungary in 1944 but his conviction was quashed by the fascist government.
Mr Kepiro returned to Hungary in 1996 after decades in Argentina. He was first accused in 2006 by Nazi hunters with the Simon Wiesenthal Center.
Mr Kepiro said he had been "the only person to refuse the order to use firearms", and that he had intervened to save five people about to be killed by a corporal.
The reliability of some of the documentary and testimonial evidence against him had also been called into question.
As he left the courtroom, Mr Zuroff said he found the verdict "outrageous, absurd" and that the Simon Wiesenthal Center would do "everything possible to see that it's overturned".
He said Mr Kepiro had "devoted all his energy to the murder of innocent men, women and children" and that the Wiesenthal Center found it "absolutely outrageous that a person like this was never punished for his crimes".
"We'll continue to do whatever we can so that Sandor Kepiro doesn't end his life sitting in peace and tranquillity... but ends his life where he belongs, in a Hungarian jail. This is a joke."
Serbian chief prosecutor Vladimir Vukcevic said he had expected a guilty verdict which would "put an end to ugly times".
"I thought it would come to the fulfilment of justice, though it did not happen. I was shocked at the behaviour in the court and the fact that the verdict was greeted with applause," he said. "It was a nauseating scene."
Teodar Kovac, a survivor of the Novi Sad killings, said he was in distress and shock over the verdict.
"I am sure that the majority of people from Novi Sad feel the same, especially those who lost members of their families in the biggest massacre in this part of Europe at that time."
Prosecutors and defence lawyers have until Friday to lodge an appeal, the Associated Press reports.