There was no immediate report of any damage to life or property due to quake which hit the prefecture and its vicinity at 8.08 am (local time). Residents in Tokyo also felt the jolts as buildings in the Japanese capital shook for several seconds.
No tsunami warning was issued, but the runways of Narita international airport in the prefecture were reportedly closed for checks in the wake of quake.
Another aftershock hit of 5.5 magnitude hit Nagano Prefecture in central Japan at 7.26 am today, the MeT officials said. The was no report of any damage.
Yesterday, a strong aftershock of magnitude 7.1 jolted Japan's northeast on the one-month anniversary of the devastating quake and tsunami that had left thousands of people dead, prompting authorities to evacuate workers from the crippled Fukushima nuclear plant.