Anti-fascist activists in Hungary have held a rally outside the last known location of a suspected Nazi war criminal ranked atop a Jewish rights group's list of Nazi aides still known to be alive.

The Simon Wiesenthal Centre, a Jewish human rights organisation, said it had tracked down Laszlo Csatary to a building in Budapest.

Activists from the European Union of Jewish Students organisation pasted "No Nazi" symbols and the protest slogan, "we never forget", to the door of Csatary's hideaway building on Monday.

The protest came after a Hungarian prosecutor said that investigating an aged Nazi war criminal found alive and well in Budapest was problematic because the events took place so long ago and in a different country.

The 97-year-old Csatary is listed by the Vienna-based Wiesenthal Centre as having "helped organise the deportation to Auschwitz of approximately 15,700 Jews" from Nazi-occupied Czechoslovakia.

The centre said its director Efraim Zuroff had submitted new evidence last week to the prosecutor in Budapest regarding crimes committed by Csatary during World War II.

"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 a statement.

The centre said the evidence "related to Csatary's 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".

It urged Hungarian prosecutors to put Csatary on trial, charging he had served during World War II as a senior Hungarian police officer in the Slovakian city of Kosice, then under Hungarian rule.

The centre said Csatary had been photographed and filmed in Budapest last September.

He was located after a tip-off, for which the informant would be paid $25,000 "if the Nazi criminal is convicted and sentenced," Zuroff told the AFP news agency.

Hungary's assistant prosecutor general, Jeno Varga, said: "An investigation is under way. The prosecutor's office will study the information received".