A man who could be one of the last people tried in Germany for Nazi-era war crimes has been found guilty of helping to kill Jews at Sobibor concentration camp.

John Demjanjuk was accused of being an accessory to the deaths of more than 27,000 people while he was a concentration camp guard during the Holocaust.

A judge sentenced him to five years in prison.

Demjanjuk, now 91, went on trial in Munich almost 18 months ago, but the proceedings were delayed because of questions about his health.

His lawyer claimed Demjanjuk, who was born in the Ukraine and served in the Red Army before 1942, was a victim of the Nazis.

However the prosecution argued he agreed to serve as a Nazi guard and called for conviction and a six-year prison sentence.

After the war Demjanjuk emigrated to Ohio and built a career as a mechanic, before being deported and sentenced to death in Israel in 1988.

The sentence was later overturned on the grounds of mistaken identity, but after more paperwork was discovered he was deported to Germany to face trial.

Demjanjuk's lawyers said they would appeal the sentence.

Elan Steinberg, vice-president of the American Gathering of Holocaust Survivors and their Descendants, welcomed the verdict.

"Humanity owed this to the memory of the tortured and the dead," he said. "His conviction is a clarion pronouncement that the pursuit of justice should know no barriers of time and geography."

Ronald Lauder, president of the world Jewish Congress, said Demjanjuk had been given a mild sentence "considering his actions at Sobibor".

Mr Lauder said: "Belatedly, justice has now been done. We praise Germany for continuing to prosecute Nazi war criminals and their helpers, and we urge authorities there – and in other European countries – not to relent in their quest for bringing the perpetrators of the Holocaust to justice.

"Demjanjuk was one of many perpetrators, and there are still a few old men out there who have the blood of innocent Shoah victims on their hands."

Avner Shalev, the chairman of Israeli Holocaust museum Yad Vashem, said holding those responsible for the Holocaust continued to have an important moral and educational role in society:

He said: "The trial and the verdict demonstrate that there is no statute of limitations on the crimes of the Holocaust."

Rabbi Marvin Hier, founder of the Simon Wiesenthal Centre praised the guilty verdict and the court for finally putting an end to his disguise and setting the record straight.

He said: "He was, in fact, one of the sadistic and brutal murderers at Sobibor. [They] sentenced him to, what for a 91-year-old man, is a life sentence in jail."

Former war crimes investigator and the chairman of the Holocaust Education Trust, Lord Janner, called the verdict "an unequivocal message that the passage of time is no barrier to justice".

"Age or poor health cannot absolve anyone of appalling crimes. Today represents a triumph of justice in the memory of the millions brutally murdered during this darkest chapter in European history."