A German judge for the first time ordered John Demjanjuk to appear in court after the 90-year-old's health issues caused the cancellation of sessions in his trial over allegations that he was a guard at the Nazis' Sobibor death camp.

Two sessions last week were called off, the last of them when the defendant suffered dehydration in hot weather, but Demjanjuk appeared Thursday at the Munich state court.

Accused Nazi death camp guard John Demjanjuk sits in a wheelchair as he arrives in a courtroom in Munich last month. Demjanjuk is accused of being a guard at a Nazi death camp. (Christof Stache/Associated Press)

Judge Ralph Alt told the court he had informed the former Ohio autoworker that he was being ordered to attend. He did not elaborate.

Demjanjuk, as he has for most of his trial, followed the hearing from a bed in the courtroom and showed no reaction to the proceedings.

Demjanjuk, who was deported from the U.S. to Germany in May 2009, is being tried on 28,060 counts of accessory to murder. He denies the charges. The defence maintains Demjanjuk was a Soviet soldier captured by the Germans and spent most of the war in prison camps himself.

Demjanjuk suffers several medical problems and more than 10 sessions have been cancelled since last November. Still, court spokeswoman Margarete Noetzel said "the judge deemed him fit for trial."

A court-appointed doctor had seen Demjanjuk before the hearing, she added.

German law only allows proceedings to be interrupted for up to four weeks, and prolonged absence by a defendant can result in a trial having to be restarted. But Noetzel said that a trial can be suspended for up to six weeks if a court-appointed doctor testifies that a defendant is ill.

Demjanjuk's lawyer, Ulrich Busch, has repeatedly called for the trial to be halted, but German doctors have declared Demjanjuk fit to face trial as long as court sessions are limited to two 90-minute sessions per day.

A doctor and paramedics have been on hand at every court session to monitor Demjanjuk's condition.

The Ukrainian-born Demjanjuk had his U.S. citizenship revoked in 1981 after the Justice Department alleged he hid his past as the notorious Treblinka guard "Ivan the Terrible."

He was extradited to Israel, where he was found guilty and sentenced to death in 1988, only to have the conviction overturned five years later as a case of mistaken identity.