BONY, Hungary — To his neighbors in a village in western Hungary, 76-year-old Istvan Gyorkos was just an old man who mostly kept to himself. Hardly anyone looked askance at his passion for guns and for training youths in paramilitary tactics.

In late October, however, Mr. Gyorkos, a veteran neo-Nazi and the leader of a tiny fringe outfit called the Hungarian National Front, suddenly took on a more sinister visage when, according to Hungarian police officers who raided his home in search of illegal weapons, he shot and killed a member of the police team with an assault rifle. Members of his family say the dead policeman was shot by a fellow officer.

The saga then took an even stranger turn: Hungarian intelligence officials told a parliamentary committee in Budapest that Mr. Gyorkos had for years been under scrutiny for his role in a network of extremists linked to and encouraged by Russia. So close was the relationship, the committee heard, that Russian military intelligence officers, masquerading as diplomats, staged regular mock combat exercises using plastic guns with neo-Nazi activists near Mr. Gyorkos’s home.

That Russia, a nation intensely proud of its huge role in the defeat of Hitler’s Germany in World War II, would want anything to do with marginal, anti-Semitic crackpots who revere Hitler’s wartime allies in Hungary might, at first glance, seem beyond comprehension.