Japanese Prime Minister Naoto Kan is urging people to move at least 20 kilometers away from the nuclear power plant where an explosion occurred Saturday.
Mr. Kan said the number one priority is the safety of the people in the areas surrounding the Fukushima plant. He said more information about the situation would be made available later Saturday.
He spoke one day after a massive magnitude 8.9 earthquake triggered a tsunami that devastated parts of Japan. He said the country had faced an “unprecedented disaster.”
In Fukushima, smoke could be seen billowing out of a building housing a nuclear reactor. Japanese media say radiation levels outside the plant rose after the blast.
The International Atomic Energy Agency says it is seeking more information on the situation. Before the explosion occurred, authorities said radioactive material had been found outside one of the plant's reactors, which had lost power and cooling abilities.
Mr. Kan earlier said 50,000 troops are joining rescue and recovery efforts across the country.
Japanese media report more than 1,300 people are dead or missing. Kyodo news agency says four trains that were traveling along the coast when the tsunami struck are missing.
Entire villages were washed away Friday by waves as high as 10 meters that carried vehicles, buildings and debris several kilometers inland. The earthquake and tsunami damaged highways and other infrastructure, further hampering rescuers' efforts to reach people stranded on the roofs and trapped in affected areas.
Japan's Tepco electric company is warning of massive power outages in the coming days across large areas of the country.
Japanese authorities said 200 to 300 bodies have been found in Sendai, the city closest to the quake, which was the most powerful on record to hit Japan and the world's fifth largest in more than a century. They say 700 people are missing and 1,000 people have been injured.
In Tokyo, the quake forced a suspension of all train and subway services, leaving millions of people stranded. Several airports were also closed, but some, including Tokyo's Narita have reopened.