What sparked rumours about Kim Jong-un's death?

North Korea's media released Kim Jong-un's images amid rumours of his death. The rumours began after US-based Chinese dissident Wanjun Xie claimed that Kim suffered 'severe cerebral haemorrhage and fell into coma'. Xie further alleged that Kim died in a Beijing hospital and his body was secretly returned to North Korea, adding, "News of...death is being kept under wraps."