A 90-year-old convicted former Nazi began serving life in prison for assassinating three civilians in the Netherlands during the Nazi occupation in 1944, AFP cited German prosecutors as saying.The former Nazi, Heinrich Boere, who confessed to being part of an SS hit squad, began serving his sentence in a prison hospital in the western German state of North Rhine-Westphalia. He had previously been tried in absentia in the Netherlands and sentenced to death, but that sentence was later commuted to life in prison.RELATED:John Demjanjuk convicted then freed by German court Jewish groups hail news of Demjanjuk guilty verdict Boere was captured by US forces in the Netherlands after the war and confessed to killing the Dutch civilians while a member of an SS death squad which hunted anti-Nazi resistance fighters.Boere, on the Simon Wiesenthal Center's list of top ten World War Two criminals, escaped and fled to Germany before being sentenced to death in absentia in the Netherlands in 1949. After refusing a 1980 Dutch extradition request, a German court indicted him in 2008. In January of the next year the case nearly collapsed after a court said he was unfit for trial, due mainly to a heart condition. The ruling was overturned by an appeal court. He was later sentenced to life in prison.