The No. 5 and No. 6 reactors at the quake-damaged Fukushima Daiichi nuclear plant went into stable condition on Sunday, local media reported.
The two reactors went into cold shutdown following restoration of cooling functions late Saturday, thanks to successful resumption of electricity supply, authorities said.
Earlier in the day the defense ministry said that it succeeded in putting water into the No. 4 reactor at the troubled Fukushima nuclear power plant.
In a separate move, the Tokyo Fire Department shot over 2,000 tons of water into a spent fuel pool of the No. 3 reactor in an overnight mission that lasted more than 13 hours until 3:40 a.m. local time Sunday.
Tokyo Electric Power Co. (TEPCO), owner and operator of the plant, was also trying to restore electricity to the No. 1 and 2 reactors to restart the cooling system.
The plant, about 220 km northeast of Tokyo, was stricken by the twin disasters of the catastrophic March 11 earthquake and ensuing tsunami.
Radioactive leaks were detected after a series of explosions and fires at four of its six reactors following the failure of their cooling functions due to the damaged power supplies.
The authorities advised residents living within 20-30 km radius of the plant to stay indoors and set the area 20 km around the plant as an exclusion zone where residents have been evacuated.