Former Cosatu general secretary Zwelinzima Vavi and EFF leader Julius Malema are plotting to overthr.
The three -- two women aged 59 and 52 and their 65 year-old brother --have denied that they conspired to abandon a body, a crime under Japanese law, because they say their 88-year-old mother is still alive.
"Our mother has become a god. She is not dead but is in the process of being elevated into a higher being," they told officers in Usa, southwestern Japan, according to Jiji Press.
A police spokesman told AFP they were awaiting final confirmation but believed the skeleton was that of a woman who would be 88 if she were still alive.
"We discovered today from an autopsy that the skeletonised body is that of a female who died two or three years ago, but we have to wait for the results if a DNA test to confirm her identity," the spokesman said.