A fire broke out at a fourth reactor in Japan's Fukushima 1 nuclear power plant Tuesday, hours after a blast ripped its third reactor. As the government said that radiation released by the damaged reactors was high enough to harm human health, Prime Minister Naoto Kan warned that further leaks were possible.

Prime Minister Naoto Kan called on citizens residing within a 20 km radius around the reactor to immediately leave the place and those living beyond that distance to stay in their houses, but to shut windows and doors, RIA Novosti reported.