Following the earthquake measuring 6.3 on the Richter scale on Sunday jolted near the east coast of Honshu, Japan, an quake of 5.6-magnitude struck the region, the U. S. Geological Survey said.

The quake, one of the aftershocks following the 8.8-magnitude quake on Friday, Struck at 07:31 local time (2231 GMT on Saturday). The epicenter, with a depth of 25.80 km, was initially determined to be at 39.2254 degrees north latitude and 142.3325 degrees east longitude.

Earthquakes measuring 5.6, 6.3, 5.3 and 5.5 respectively on the Richter scale jolted near the east coast of Honshu, Japan within one hour, according to the U.S. Geological Survey.

Amid a series of moderate and strong aftershocks struck off the east coast of Honshu since Friday, another reactor in Fukushima has also lost its emergency cooling system, Japan's nuclear power safety agency said on Sunday.

An official of the Japan Nuclear and Industrial Safety Agency told a news conference that the emergency cooling system of the No. 3 reactor is no longer functioning.

An explosion occurred at the Fukushima No. 1 nuclear power plant earlier on Saturday triggered public panic, but the Chief Cabinet Secretary Yukio Edano said late Saturday that owner and operator of the nuclear facility, Tokyo Electric Power Co., has confirmed that the steel container housing the reactor is intact.

The number of individuals exposed to radiation from the incident could reach 70 to 160, an official of Japan's nuclear safety agency said.