Japan's defense ministry said Sunday that it succeeded in putting water into the No. 4 reactor at the troubled Fukushima No. 1 nuclear power plant.

About 80 tons of water was believed to have been shot into the reactor's spent fuel pool in a 70-minute mission which ended at 9: 30 a.m. local time (0030 GMT).

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.

The cooling system was reactivated at the No. 6 reactor, thanks to restoration of electricity supply and the temperature of its overheated spent fuel pool has dropped to around 40 degrees Celsius, according to the operator Tokyo Electric Power Co.

The company is trying to restore electricity to the No. 1 and 2 reactors later Sunday to restart the cooling system.

The power plant, about 220 kilometers northeast of Tokyo, was stricken by catastrophic March 11 earthquake and ensuing tsunami, triggering a series of explosion and fire at four of its six reactors following failure of their cooling function due to damaged power supply.