Seven days after earthquake and ensuing tsunami devastated Japan, efforts to search for victims continued amid difficulties brought about by cold weather and energy shortage.

Temperatures in the quake-hit areas in northeastern Japan dropped to midwinter levels Thursday, marking 5.9 degrees below zero in Morioka, Iwate, 2.7 degrees below zero in Sendai, Miyagi, and 3.5 degrees below zero in the city of Fukushima.

Fuel shortages have hampered the delivery of relief supplies to shelters where survivors are staying, while also limiting the use of heavy machinery and heating appliances, rescuers said, according to Kyodo news agency.

The National Police Agency (NPA) said Thursday that quake and tsunami have left 5,429 people dead and 9,594 others unaccounted for in Japan by 4:00 p.m.(0700 GMT).

Around 2,000 recovered bodies were identified by 10 a.m. Thursday in Iwate, Miyagi and Fukushima prefectures, of which 870 were returned to their families, while the number of partially or completely destroyed buildings exceeded 75,000, according to the NPA.

Amid a looming nuclear crisis, Japan's Self-Defense Forces on Thursday morning used helicopters to spray water on the No. 3 reactor of the Fukushima No. 1 nuclear power plant, which was feared to have been leaking radioactive steam due to damage to its containment vessel.

Fire trucks of the Self-Defense Forces joined Thursday evening in an unprecedented mission to direct jets of water onto a stricken nuclear reactor in an effort to cool down its apparently overheating spent fuel pool to prevent radiation being emitted. But the action had no immediate effect on radiation levels there, according to the government's Nuclear and Industrial Safety Agency.

As a precaution, the Japanese government had evacuated residents from areas within a 20-km radius from the plant and advised those within a 30-km radius to stay indoors.

The number of people evacuating from Fukushima Prefecture to nearby prefectures is increasing. Niigata, Yamagata and Miyagi prefectures have accepted a total of 15,000 evacuees from outside the prefectures, Kyodo quoted local governments as saying, adding that most of them are believed to be from Fukushima.

Around 10,000 people who have visited health facilities and evacuation stations in Fukushima prefecture were tested for radiation exposure, local media reported Thursday, citing prefectural officials.

According to the reports, those tested included residents living around the quake-stricken Fukushima No. 1 nuclear plant as well as people who have survived Friday's devastating quake and tsunami in the region and have been forced to evacuate to community shelters.

Following the radiation leak at the plant operated by the beleaguered Tokyo Electric Power Co. (TEPCO), six people were treated for exposure to radiation, following tests conducted at 26 screening locations.

The Japanese government on Thursday announced the possibility of a large-scale power outage in the Tokyo area as demand in the area may outstrip supply while temperatures fall in the evening.

To avoid the massive power failure, the Land, Infrastructure, Transport and Tourism Ministry issued an emergency instruction to railway operators in the metropolis to reduce their services to conserve power during the evening, as the commuter rush would cause electricity levels to peak.

Economy, Trade and Industry Minister Banri Kaieda said a massive blackout could occur even though TEPCO carried out planned power outages Thursday for the fourth straight day in part of the Kanto region, including Tokyo.