SOMA, Japan - (AP) - Radiation leaked from a crippled nuclearplant in tsunami-ravaged northeastern Japan after a third reactorwas rocked by an explosion Tuesday and a fourth caught fire in adramatic escalation of the four-day-old catastrophe. The governmentwarned anyone nearby to stay indoors to avoid exposure. In a nationally televised statement, Prime Minister Naoto Kansaid radiation has spread from four reactors of the FukushimaDai-ichi nuclear plant in Fukushima province, one of thehardest-hit in Friday's 9.0-magnitude earthquake and the ensuingtsunami. "The level seems very high, and there is still a very high riskof more radiation coming out," Kan said. "We are making utmostefforts to prevent further explosions and radiation leaks." This is the worst nuclear crisis Japan has faced since theatomic bombing of Hiroshima and Nagasaki during World War II. It isalso the first time that such a grave nuclear threat has beenraised in the world since a nuclear power plant in Chernobyl,Ukraine exploded in 1986. Kan warned there are dangers of more leaks and told peopleliving within 19 miles of the Fukushima Dai-ichicomplex to stay indoors to avoid radiation sickness. Some 70,000people had already been evacuated from a 12-mile radius and 140,000 remain in the zone for which the new warning wasissued. Three reactors at the power plant were in critical conditionafter Friday's quake, losing their ability to cool down andreleasing some radiation. A fourth reactor that was unoperationalcaught fire on Tuesday and more radiation was released, ChiefCabinet Secretary Yukio Edano said. The fire was put out. Even though it was unoperational, thefourth reactor was believed to be the source of the elevatedradiation release because of the hydrogen release that triggeredthe fire. "It is likely that the level of radiation increased sharply dueto a fire at Unit 4," Edano said. "Now we are talking aboutlevels that can damage human health. These are readings taken nearthe area where we believe the releases are happening. Far away, thelevels should be lower," he said. "Please do not go outside. Please stay indoors. Please closewindows and make your homes airtight. Don't turn on ventilators.Please hang your laundry indoors," he said. He said a reactor whose containment building caught fire Mondayhas not contributed greatly to the increased radiation. Theradiation level around one of the reactors stood at 400,000microsiverts per hour, four times higher than the safe level. Officials said 50 workers were still there trying to put waterinto the reactors to cool them. They say 800 other staff wereevacuated. The fires and explosions at the reactors have injured 15workers and military personnel and exposed up to 190 people toelevated radiation. In Tokyo, slightly higher-than-normal radiation levels weredetected Tuesday but officials insisted there are no healthdangers. The death toll from last week's earthquake and tsunami jumpedTuesday as police confirmed the number killed had topped 2,400,though that grim news was overshadowed by a deepening nuclearcrisis. Officials have said previously that at least 10,000 peoplemay have died in Miyagi province alone. Links and information to help with Japan quake victims