Is self-immolation an ethical act?

The image of the Buddhist Monk Thich Quang Duc committing suicide by self-immolation is a hugely iconic image of the 20th century. But bearing in mind the first precept against taking life, can this be considered an ethical act in the context of Buddhism. I appreciate that as a political act it was brave and significant. Since Thich Quang Duc was a committed Buddhist I would imagine that he was pretty certain it was in keeping with Buddhist ethics. What was his line of reasoning? Is there precedent in scripture for this kind of act?