"This is the largest earthquake since the Meiji Era (1868-1912), and it is believed that more than 1,000 people have lost their lives," Chief Cabinet Secretary Yukio Edano said at a meeting at the emergency disaster headquarters, a day after the monster 8.9-magnitude tremor struck, unleashing a devastating tsunami.
He expressed his government's determination to bring relief to the disaster-hit areas.
In Fukushima Prefecture, there were reports that radiation 1,000 times above normal was detected in the control room of one nuclear plant, although officials said levels outside its gates were only eight times above normal and asserted that were no health hazards as of now.
The Nuclear and Industrial Safety Agency said it issued an unprecedented order for the electricity firm running the atomic unit to open a valve at the plant to release pressure in the container housing the reactor following the powerful earthquake.
The local government, acting on orders from Prime Minister Naoto Kan, instructed about 3,000 residents living within a 10-kilometer radius of the No 1 nuclear plant in the region and within a 3-kilometer radius of the No 2 plant to evacuate.
A state of emergency was declared at two reactors at Japan's Daiichi and three units at its nearby Fukushima Daini site, media reports said.
The National Police Agency was quoted by Kyodo as saying that the total number of those died and were unaccounted for in yesterday's catastrophic earthquake topped 1,000, as some areas suffered devastating damage mainly due to tsunami waves of up to 33-foot high.
Four trains running in a coastal area of Miyagi and Iwate prefectures remained unaccounted for, the train operator said.
It is not known how many people were aboard the trains that were running on East Japan Railway Co.'s Ofunato, Senseki and Kesennuma lines on the Pacific coast when the quake hit northern Japan.
The company said earlier that another train on the Senseki Line was found derailed near Nobiru Station after the quake. The Miyagi prefectural police today rescued nine passengers from the train by helicopter, Kyodo said.
The number of partially or completely destroyed buildings reached 3,400, while there 200 incidents of fire at quake-affected areas. Some 181 welfare facilities, including nursing homes, had been damaged.