A German court has sentenced John Demjanjuk to five years in prison for his role in the killing of 27,900 Jews at the Nazi death camp at Sobibor.
His lawyers will appeal the verdict.
The Munich court found the 91-year-old guilty of being an accessory to mass murder as a guard at Sobibor camp in Nazi-occupied Poland during the second World War.
Demjanjuk was charged with 28,060 counts of being an accessory to murder, one for each person who died during the time he was accused of being a guard at the camp.
There was no evidence he committed a specific crime. The prosecution was based on the theory that if Demjanjuk was at the camp, he was a participant in the killing - the first time such a legal argument has been made in German courts.
Demjanjuk sat in a wheelchair in front of the judges as they announced their verdict, but showed no reaction. Earlier he had declined the opportunity to make a final statement to the court.
"The court is convinced that the defendant ... served as a guard at Sobibor from March 27th 1943 to mid September 1943," presiding Judge Ralph Alt said as he announced the verdict.
The verdict will not entirely end more than 30 years of legal wrangling. The defence has pledged to appeal and legal proceedings continue in the United States.
In the 1980s, Demjanjuk stood trial in Israel after he was accused of being the notoriously brutal guard "Ivan the Terrible" at the Treblinka extermination camp. He was convicted, sentenced to death - then freed when an Israeli court overturned the ruling, saying the evidence showed he was the victim of mistaken identity.
Demjanjuk maintains he was a victim of the Nazis - first wounded as a Soviet soldier fighting German forces, then captured and held as a prisoner of war under brutal conditions before joining the Vlasov Army, a force of anti-communist Soviet POWs and others which was formed to fight with the Germans against the Soviets in the final months of the war.
Holocaust survivors welcomed the guilty verdict, as did the Nazi-hunting Simon Wiesenthal Centre, where Rabbi Marvin Hier said: "John Demjanjuk's Nazi past finally caught up with him."
"Humanity owed this to the memory of the tortured and the dead," Elan Steinberg of the American Gathering of Holocaust Survivors and their Descendants said. "His cynical manipulation of the legal system has at last been ended".
Ukraine-born Demjanjuk said he was drafted into the Soviet army in 1941 then taken prisoner of war by the Germans.
Demjanjuk attended the 18-month court proceedings in Munich - birthplace of Adolf Hitler's Nazi movement - in a wheelchair and sometimes lying down, with his family trying to argue that he was too frail to stand trial.
His son, John Demjanjuk Jr, said his father was a victim of the Nazis and of post-war Germany. "While those who refuse to accept that reality may take satisfaction from this event, nothing the Munich court can do will atone for the suffering Germany has perpetrated upon him to this day," he said.
Prosecutors had faced several hurdles in proving Demjanjuk's guilt, with no surviving witnesses to his crimes and heavy reliance on wartime documents, namely a Nazi ID card that defence attorneys said was a forgery made by the Soviets.
Guards at Nazi death camps like Sobibor were essential to the mass killing of Jews because extermination was the focus of such camps, prosecutors said. Some 250,000 Jews were killed at Sobibor, according to the Wiesenthal Centre.
Defence attorney Ulrich Busch told the court yesterday that even if Demjanjuk did become a prison guard, he did so only because as a prisoner of war he would have either been shot by the Nazis or died of starvation.
Demjanjuk emigrated to the United States in the early 1950s and became a naturalised citizen in 1958, working as an engine mechanic in Ohio.
Agencies