At least 20 aftershocks, from 5-6.8 magnitude on the Richter scale, jolted near the east coast of Honshu, Japan Saturday following a massive 8.8 magnitude earthquake struck the country Friday afternoon.

At least 630 people were killed after Friday's great earthquake and ensuing huge tsunami hit northeast Japan, public broadcaster NHK reported Saturday.

According to the National Police Agency, more than 215,000 people were in emergency shelters in eastern and northern Japan on Saturday following the 8.8 magnitude earthquake and tsunami struck the country.

The number included more than 100,000 people who took refuge in the northern prefecture of Fukushima, including residents evacuated from two nuclear power plants after the confirmed leakage of radioactive materials. According to NHK news reports, the death toll from Friday's powerful quake in Japan reached 576 and over 725 were missing Saturday following some areas suffered devastating damage in the 8.8 magnitude earthquake, the strongest ever recorded in Japan.

The devastating damaged caused by the quake that struck at 2:46 p.m. (0546 GMT) on Friday was amplified by tsunami waves devouring Pacific coastal regions in northeastern Japan.

A total of 725 people have still been unaccounted for in six prefectures following the 8.8 magnitude earthquake that could be felt in most regions of the nation.

As all the available Self Defense Force (SDF) resources were mobilized to provide emergency relief Saturday, the number of victims of the catastrophe is expected to rise to well over 1,000 people, the NPA and Defense Ministry said Saturday.

Up to 300 bodies were recovered in Sendai, the capital city of Miyagi Prefecture and the largest city in the Tohoku Region, official said and the Pacific-facing Wakabayashi area of the city was totally leveled by tsunami waves destroying 1,200 homes.

The coastal city of Rikuzentakata in Iwate Prefecture was also devastated by a tsunami wave. Traveling in-bound at speeds upwards of 500 kilometers per hour, the city was completely engulfed, the Fire and Disaster Management Agency said.

The National Police Agency said around 1,800 houses in Fukushima Prefecture were destroyed.

"More than 90 percent of the houses in three coastal communities have been washed away by tsunami. Looking from the fourth floor of the town hall, I see no houses standing," a city official from Futaba, Fukushima Prefecture, was quoted as saying.

Japan's search and rescue efforts are being conducted with the help of the U.S. military, with around 20,000 SDF personnel, nearly 200 aircraft and 25 boats being dispatched to the hardest- hit northeastern regions.

Rescue helicopters are attending to 80 people stranded on ship in the waters off Ishinomaki, Miyagi Prefecture and have airlifted people to safety from an elementary school in the town of Watari, in Miyagi, local reports said.

Rescue teams from foreign countries are due to arrive in Japan from Saturday to provide further man power.

The Foreign Ministry said Saturday that 50 nations and regions have offered to provide support following Friday's mega-quake.

Almost 6 million households were left without power in quake- hit regions Saturday and four trains operating in the coastal regions of Miyagi and Iwate prefectures have yet to be found following the colossal tsunami.

The local railway company said another train was derailed and nine people had to be airlifted to safety on Saturday.

The Nuclear and Industrial Safety Agency is monitoring two faltering power plants in Fukushima Prefecture and local residents have been evacuated from the vicinity of the facilities.

At Fukushima's No. 1 plant, the amount of radiation reached 1, 000 times the regular level in the operating room, the agency said and the No. 2 plant is set to release pressure in containers housing nuclear reactors that could result in the leak of radioactive substances.

The failsafe system at the No. 2 plant stopped functioning as the temperature of coolant water exceeded 100 C, the agency said.

Prime Minister Naoto Kan on Saturday inspected a quake-hit nuclear power plant in Fukushima Prefecture, where damage from a radioactive leak is feared, and toured other affected areas.

The Nuclear and Industrial Safety Agency said Saturday that radioactive cesium has been detected at Fukushima No. 1 nuclear power plant.

Agency officials said the detection indicates a reactor meltdown is about to occur.

The operator of the Fukushima No. 1 nuclear plant opened the valves of the containers housing the reactors to reduce pressure, a move that led to the release of a small amount of radioactive steam.

According to the Tokyo police more than 116,000 people were unable to return to their homes on Friday evening due to train services being halted and heavy traffic.

JR East will continue the suspension of bullet train services on the Tohoku Shinkansen Line through Saturday, the company said.

People in the capital and nine other prefectures were stuck in 163 elevators following Friday's quake, with 88 of them being rescued thus far, the Land, Infrastructure, Transport and Tourism Ministry said Saturday.

Japanese Foreign Ministry said Saturday that rescue teams from foreign countries are set to begin arriving in Japan from Saturday after 50 countries and regions offered support following Friday's powerful earthquake.