A probe into Laszlo Csatary, 97, began in September after information was received from the Nazi-hunting Simon Wiesenthal Center, which ranks him number one on their wanted list, the public prosecutors' office said.

The investigation covered events in 1944 in Kosice, then in Hungary but now in Slovakia, where the Wiesenthal Center says as a senior policeman he helped organise the deportation to the Auschwitz death camp of some 15,700 Jews.

The investigation "therefore has to explore an event remote in both time and place," with "significant part" of the probe dedicated to finding possible witnesses, some of whom may live abroad, prosecutors said.

"It took place 68 years ago in an area that now falls under the jurisdiction of another country -- which also with regard to the related international conventions raises several investigative and legal problems," a statement said.

"Finding the answers to the aforementioned questions is a precondition to clarifying the facts and determining further investigative actions."

In 1948, a Czechoslovakian court condemned Csatary to death in absentia but he had made it to Canada where he worked as an art dealer in Montreal and Toronto until he was stripped of his citizenship and was forced to flee in 1997.

He ended up in Budapest where he lived undisturbed until the Wiesenthal Center alerted Hungarian authorities last year. British tabloid The Sun in a report at the weekend tracked down the old man and confronted him.

"No, no. Go Away," the paper quoted him as saying at the door to his apartment.

Efraim Zuroff, the Wiesenthal Center's chief Nazi-hunter, handed over more evidence to Hungarian prosecutors last week highlighting Csatary's "key role" in the 1941 deportation of some 300 Jews from Kosice to Ukraine, most of whom were murdered.

Zuroff told AFP on Sunday that he has been "very upset and very frustrated" about the lack of action by Hungarian authorities.

"Something has to be done because he's in good health at 97... but this could change very quickly."

"The passage of time in no way diminishes his guilt and old age should not afford protection for Holocaust perpetrators."

French Nazi-hunter Serge Klarsfeld said on Monday he doubted Hungarian authorities would prosecute Csatary, even as Paris urged Budapest to launch legal proceedings against him.

The Hungarian government of right-wing Prime Minister Viktor Orban declined to comment on the case, saying it was a matter for the public prosecutor's office.

"The Hungarian government has always supported the exhaustive exploration of past crimes and the prosecution of perpetrators," said spokeswoman Judit Pach.

"Therefore, it calls for the exploration of the truth and the punishment of the guilty."