The International Atomic Energy Agency, based in Vienna, says the people were ordered out of a 12-mile (20-kilometer) radius surrounding the Fukushima Dai-ichi plant.
The plant exploded Saturday, destroying the building housing the reactor but not the reactor itself, and complicating relief and rescue efforts by authorities after Friday's twin disasters.
The IAEA says another 30,000 people were moved away from the area around a second nuclear plant.
Japan launched a massive, military-led rescue operation Saturday after a giant quake and tsunami killed hundreds of people and turned the northeastern coast into a swampy wasteland as authorities braced for a possible meltdown at a nuclear reactor.
Prime Minister Naoto Kan said he is sending 50,000 troops for the rescue and recovery efforts following Friday's 8.9-magnitude quake that unleashed one of the greatest disasters Japan has witnessed - a 23-foot (7-meter) tsunami that washed far inland over fields, smashing towns, airports and highways in its way.
The official death toll stood at 413, while 784 people were missing and 1,128 injured. In addition, police said between 200 and 300 bodies were found along the coast in Sendai, the biggest city in the area near the quake's epicenter. An untold number of bodies were also believed to be lying in the rubble and debris. Rescue workers had yet to reach the hardest-hit areas.
Adding to the worries was the damage at the Fukushima Dai-ichi nuclear power plant, where two reactors had lost cooling ability.
Because of the overheating, a meltdown was possible at one of the reactors, said Ryohei Shiomi, an official with Japan's nuclear safety commission.
But even if there was a meltdown, it wouldn't affect humans outside a six-mile (10-kilometer) radius, he said.
More than 215,000 people were living in 1,350 temporary shelters in five prefectures, or states, the national police agency said. Since the quake, more than 1 million households have not had water, mostly concentrated in northeast.
Kan said a total of 190 military planes and 25 ships have been sent to the area.
"Most of houses along the coastline were washed away, and fire broke out there," he said after inspecting the quake area in a helicopter. "I realized the extremely serious damage the tsunami caused."
