According to the U.S. Geological Survey, a 6.0 magnitude earthquake hit Japan's east coast of Honshu at 11:54:41 AM at epicenter. The depth of the quake was 7 km.
Casualties and damages are unknown so far. More details are awaited.
Meanwhile, Japan expanded the evacuation zone to 20 km around the Fukushima Daiichi nuclear plant north of Tokyo.
On Apr 11, Japan was hit by strong earthquake shocks struck off the country's northeast coast, killing one person and triggering a tsunami warning.
The first quake had a magnitude of 6.6 and caused a temporary loss of external power at the Fukushima Daiichi atomic power station. According to local television reports, elsewhere in the Fukushima prefecture, several cars with passengers were engulfed in a landslide.
Twenty-five aftershocks followed the quake, centred 88 km west if the crippled Fukushima power station and power supplies to 220,000 households were knocked out as building swayed in Tokyo and other parts of eastern Japan.
Japan is already reeling from the 9.0 earthquake, the biggest in the quake-prone country's recorded history, that struck on Mar 11 triggering a 10-metre high tsunami and a major nuclear crisis, causing millions of dollars in damages and leaving about 28,000 people dead or missing.
Meanwhile, Tokyo Electric Power Co (TEPCO), the operator of the plant, said it had completed its controlled discharge of radiated sea-water some of which was used to cool reactors after their cooling systems failed and the rest brought in by the tsunami.
The company had said it had pumped out 10,400 tonnes of low-level radioactive water, amid contamination concerns raised by China and South Korea. Authorities also said that children, pregnant women, and hospitalised patients should avoid a radius of 20-30 km from the atomic station.