British historian David Irving has pleaded guilty in a court in Vienna to charges of denying the Holocaust.
David Irving arrived at court carrying a copy of one of his books
"I made a mistake when I said there were no gas chambers at Auschwitz," he told the court, referring to comments he made in Austria in 1989.
But he insisted: "In no way did I deny the killings of millions of people by the Nazis."
Mr Irving, 68, faces up to 10 years in jail in Austria, where Holocaust denial is a criminal offence.
Fears that the court case would provoke right-wing demonstrations and counter-protests did not materialise, the BBC's Ben Brown at the court in Vienna said.
Mr Irving arrived in the court room handcuffed, wearing a blue suit, and carrying a copy of Hitler's War, one of many books he has written on the Nazis, and which challenges the extent of the Holocaust.
Mr Irving was arrested in November when he went to Austria to give a lecture to a far-right student fraternity. He has been held in custody since then.
He was stopped by police on a motorway in southern Austria, on a warrant dating back to 1989, when he gave a speech and interview denying the existence of gas chambers at Auschwitz.
In the past, he has claimed that Adolf Hitler knew little, if anything, about the Holocaust, and that the gas chambers were a hoax.
In 2000, a British court threw out a libel action he had brought, and declared him "an active Holocaust denier... anti-Semitic and racist".
On Monday, before the trial began, he told reporters: "I'm not a Holocaust denier. Obviously, I've changed my views.
"History is a constantly growing tree - the more you know, the more documents become available, the more you learn, and I have learned a lot since 1989."
Asked if he admitted the existence of the Holocaust, he replied: "I would call it the Jewish tragedy in World War II."
"Yes, there were gas chambers," he said. "Millions of Jews died, there is no question. I don't know the figures. I'm not an expert on the Holocaust."
Plea for leniency
Of his guilty plea, he told reporters: "I have no choice."
He said it was "ridiculous" that he was being tried for expressing an opinion.
"Of course it's a question of freedom of speech... I think within 12 months this law will have vanished from the Austrian statute book," he said.
Mr Irving's lawyer, Elmar Kresbach, told the BBC that he would be asking for "a certain leniency in sentencing".
"His lecture happened 17 years ago. He is an English citizen, he doesn't live in Austria, [he is] 68-years-old. He is a historian who is well known. He is not really dangerous, especially in Austria," he said.