An earthquake measuring at least 5.7 struck Japan's quake-stricken Fukushima region on Saturday, but there were no initial reports of casualties or damage, DPA reported.
National meteorological officials in Tokyo put the quake at 5.7- magnitude, although measurements taken in the United States were given as 6.2.
The quake's epicentre was some 30 kilometres beneath the Pacific. No tsunami warning was issued.
Japan's Fukushima region was devastated by a massive 9.0-magnitude quake followed by a tsunami on March 11, and since then the area has been shaken by hundreds of follow-up tremors.