What is the ruling on relieving oneself in a Muslim cemetery?

This act is abominable, reprehensible, and an assault on the sanctity of the deceased, for the grave is to the dead what the house is to the living. The Prophet, peace and blessings be upon him, clarified the atrocity of this act by saying: "For me to walk on a burning coal or a sword, or to mend my sandal with my foot, is more beloved to me than to walk on the grave of a Muslim. And I do not care whether I relieve myself in the middle of the graves or in the middle of the marketplace."