Close-up pictures of the devastated No 4 reactor building show the gaping hole through which radiation is escaping into the atmosphere as the rods break down.
Last night, the UN's nuclear safety body said it was "too early to say" whether desperate attempts to cool them by spraying water into the building had been a success.
The Foreign Office issued an urgent statement advising any Britons within 50 miles of the plant to leave the area immediately, and arranged charter flights to get British citizens out of the country.
Radiation levels 20 miles from the plant – well outside Japan's official 12-mile evacuation zone – came close to double the safety limit normally allowed for nuclear workers.
Despite assurances that other countries were not at risk of harmful levels of radiation, growing alarm led to panic-buying of radiation-blocking drugs in places thousands of miles from Japan.