SHATTERED Japan is braced for a fresh quake nightmare - with a mega aftershock likely to hit at any moment.
The alert was issued as millions who survived the tsunami that devastated the hi-tech superpower spent a third day without food and water - let alone electricity.
Japan's world-renowned centre for earthquake prediction said there was a seven-in-ten chance of a tremor with a magnitude of seven or more hitting "within the next three days".
Director Takashi Yokota confirmed as a VOLCANO piled on the misery for wretched victims of Friday's catastrophe: "There is a 70 per cent possibility."
The heartbreaking warning raised the spectre of another tsunami like the one that was last night feared to have killed up to 20,000.
Early today there was a hydrogen blast inside No3 reactor at the stricken Fukushima nuclear plant.
Tokyo Electric Power Company said 11 workers were injured after the explosion. Seven people were also reported as missing.