(CNN) -- A worldwide Jewish rights organization is pushing Hungarian authorities to prosecute a man it claims is a Nazi war criminal, recently discovered in Budapest, Hungary, who allegedly sent more than 15,000 Jews to Auschwitz in the spring of 1944.
The Simon Wiesenthal Center found Ladislaus Csizsik-Csatary as part of its "Last Chance" project, said Efraim Zuroff, director of the center's Israel office.
The center cooperated with British tabloid The Sun to photograph Csizsik-Csatary, who reportedly is 97, and ask him questions, Zuroff said. "We're the ones who found him; they're the ones who photographed him."
Csizsik-Csatary served as a senior Hungarian police officer in the city of Kosice, which is now in Slovakia but was under Hungarian rule in the 1940s, the center said. He topped the Wiesenthal Center's 2012 list of most wanted Nazi war criminals.
"He was a commander of a ghetto," Zuroff told CNN.
Csizsik-Csatary participated in the deportation of 15,700 Jews to the Auschwitz concentration camp in 1944, witnesses have told the center. He also played a role in "deportations to the Ukraine to be killed -- 300 Jews," Zuroff said.
"We found eyewitnesses on three different continents," Zuroff said. Those witnesses told the center about Csizsik-Csatary's cruelty to Jewish detainees and his role in the deportations to Auschwitz and Ukraine.
Confronted by a Sun reporter, Csizsik-Csatary denied the allegations, the tabloid reported Sunday.
A witness to the August 1941 Ukraine deportations had nine family members who were deported, he told CNN. Csizsik-Csatary made sure four of them were brought back from forced labor with the Hungarian army so they would be deported and killed, according to Zuroff.
During the Auschwitz deportations, Csizsik-Csatary "forced these girls to dig a ditch with their hands -- young Jewish girls." Two of the center's witnesses were survivors of that deportation, he said.
According to The Sun, which cited documents released by the Wiesenthal Center, Csizsik-Csatary beat Jewish women with a whip he carried on his belt.
"A variety of factors" led to the center's locating Csizsik-Csatary in Budapest, Zuroff said. "He wasn't hiding under a false name. ... He had no reason to fear."
Using the last name Csizsik, Csizsik-Csatary arrived in Canada in 1949, telling immigration officials he was Yugoslavian, according to The Toronto Star newspaper.
A spokeswoman for Canada's Department of Justice, Carole Saindon, said Monday that "It was alleged that when applying to immigrate to Canada, (Csizsik-Csatary) provided false information about his nationality, and failed to provide information concerning his collaboration with Nazi occupation forces while serving with the Royal Hungarian Police. It was further alleged that he participated in the internment and deportation of thousands of Hungarian Jews to concentration camps. As a result, the government of Canada revoked his citizenship on August 28, 1997.
As deportation proceedings were under way, Csizsik-Csatary voluntarily left the country, Saindon said in an e-mail to CNN.
In October 1997, Paul Vickery, head of the Canadian Justice Department's war crimes unit, told Radio Free Europe that when officials went to Csizsik-Csatary's Toronto home, his daughter told them he was living in Europe. Vickery told the network Csizsik-Csatary's name would be placed on a watch list and he would be barred from re-entering Canada.
Csizsik-Csatary initially denied the allegations and asked the Canadian government to put the case on trial, but later withdrew that request, The Toronto Star reported in August 1997.
"In his statement of defense, Csizsik-Csatary admitted to some involvement in the ghettoization of Jews, to handing over at least two Jews to the Germans and to attending the last mass deportation of Jews out of Kassa (Hungary)," the Star said.
The Sun said in its Sunday report that Csizsik-Csatary's attorneys claimed he did not know where the Jews were being sent. Of the 12,000 Jews transferred from a ghetto to a brickyard and deported, only 450 survived, the Sun reported.
Csizsik-Csatary returned to Hungary upon leaving Canada, Zuroff said. "Hungarian authorities knew that he was back," he said. Authorities in Hungary launched an investigation in September 2011 after receiving information from Zuroff regarding Csizsik-Csatary's residence in Budapest and his role in the Auschwitz deportations, the center said.
The Sun reported Sunday that when a reporter knocked on the door of Csizsik-Csatary's two-bedroom Budapest apartment and asked him if he could justify his past, "He looked shocked and stammered, 'No, no. Go away.'"
Asked about the deportation case in Canada, the Sun said he replied, "No, no, I don't want to discuss it."
The Sun reporter asked, "Do you deny doing it? A lot of people died as a result of your actions," according to the report.
Csizsik-Csatary replied, "No, I didn't do it. Go away from here," and slammed the door, according to the newspaper.
The Simon Wiesenthal Center said in a statement Sunday that Zuroff last week submitted new evidence to a Budapest prosecutor regarding Csizsik-Csatary and his "key role in the deportation of approximately 300 Jews from Kosice to Kamenetz-Podolsk, Ukraine, where almost all were murdered in the summer of 1941."
"This new evidence strengthens the already very strong case against Csatary and reinforces our insistence that he be held accountable for his crimes," Zuroff said in the statement. "The passage of time in no way diminishes his guilt and old age should not afford protection for Holocaust perpetrators."
Csizsik-Csatary reportedly was convicted of war crimes in absentia and sentenced to death in 1948 in the Czech Republic, Zuroff said, but the center has not obtained documentation on the case.
CNN's Ben Brumfield and journalist Flora Hevesi contributed to this report.