Far-right German activist and Holocaust denier Ernst Zundel has died at the age of 78, according to media reports.

CBC says Zundel died Sunday at home in Germany's Black Forest region after he was found unconscious by his sister Sigrid.

The cause of death was a heart attack, according to his wife, Ingrid. She said that Zundel died at the home in the Black Forest in Germany where he was born.

Born in Germany in 1939, Zundel immigrated to Canada in 1958 and for decades promoted Nazi propaganda through pamphlets and a website devoted to denying the Holocaust.

While he was living in Toronto and Montreal, Canadian officials twice rejected Zundel's attempts to obtain Canadian citizenship, and he moved to Pigeon Forge, Tennessee. He was deported to Canada from the U.S. in 2003 for alleged immigration violations.

The literature he published was twice ruled as hateful and in 2005, Zundel was declared a national security threat by a Federal Court judge, clearing the way for his deportation to Germany that year.

In February 2007, Zundel was convicted in Germany for 14 counts of inciting hatred for years of anti-Semitic activities, including contributing to a website devoted to denying the Holocaust.

Upon his conviction in Germany in 2007, the chief executive officer of the Canadian Jewish Congress called Zundel “one of the most renowned hate-mongers.”

“That will be his final epitaph,” Bernie Farber said.

He spent an additional number of years behind bars on the German warrant after having been deported from the United States for alleged immigration violations.

He was released in 2010.

Zundel's supporters were known to argue that he was exercising his right to free speech.

Supporters outside the prison in Mannheim called Zundel “a brave man” and “a victim of justice,” while some maintained there still was no evidence that anyone was gassed to death at Nazi concentration camps during the Second World War.

In March, the U.S. Department of Homeland Security's administrative appeals office, denied an application of E.C.Z., whose initials and supporting details led the Washington Post to conclude it was Zundel.

Zundel had applied for an immigrant visa to move to the United States with his wife of 16 years, a U.S. citizen. But he was classified as inadmissible because he has been convicted of foreign crimes for which the sentence was five years or more.

His controversial works continued to be felt even after his deportation. In March, Indigo Books & Music pulled two books from its online inventory that praise Hitler and question the Holocaust.

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One of the books, The Hitler We Loved and Why, was co-written by Zundel under the pseudonym Christof Friedrich.

With files from The Associated Press and The Canadian Press