LONDON — An 81-year-old former Marxist urban guerrilla who became a far-right extremist and was sentenced to 10 years in prison for Holocaust denial was arrested in Hungary on Monday after illegally leaving Germany, officials said.
The German news media reported that the extremist, Horst Mahler, had announced he was seeking asylum in Hungary, where the rightist government of Prime Minister Viktor Orban has repeatedly provoked the European Union with crackdowns on the press, political opponents, refugees, judges and academic institutions.
Ken Heidenreich, a spokesman for the prosecutor’s office in Munich, said in a telephone interview that his office had been informed that Mr. Mahler had been arrested in Hungary.
Hungarian officials initially said that they did not know about any arrest or asylum request, adding that if Mr. Mahler applied for asylum, he would be rejected, because he is a citizen of a European Union member country — namely, Germany.
On Monday afternoon, however, the police in Hungary announced that Mr. Mahler had been detained in Sopron, a city in the west of the country, near the border with Austria. Officials said it was likely he would be returned to Germany.
The arrest added a wrinkle to the case of Mr. Mahler, a bizarre figure. Once part of the extreme left that violently opposed residual Nazi tendencies in Germany, he is now known for anti-Semitic and anti-American rants.
Mr. Mahler was born in 1936 in what was then Haynau, in the German territory of Silesia, a town now called Chojnow, in southwestern Poland. His parents were Nazi Party members, even though Mr. Mahler had Jewish ancestors.
Trained as a lawyer, he joined the center-left Social Democratic Party, which later expelled him. In the late 1960s, he became prominent in leftist circles and represented, among others, the Nazi hunter Beate Klarsfeld, the left-wing activist Fritz Teufel, the student leader Rudi Dutschke and Andreas Baader, a leader of the Baader-Meinhof Gang, later known as the Red Army Faction. He was active in the movement against the Vietnam War and against Axel Springer, the powerful publishing company that runs two top-selling German newspapers, Bild and Die Welt.
In 1974, he was sentenced to prison for bank robberies in connection with the Red Army Faction. In the 1990s, he moved decisively to the right, joining the xenophobic National Democratic Party in 2000; the newspaper Süddeutsche Zeitung once described him as the “chief ideologue of the radical wing” of the party.