TOKYO, May 8 (Xinhua) -- Six people were slightly injured in a strong earthquake which jolted a wide range of areas in eastern Japan's Kanto region early Thursday morning.

    It briefly cut off power to some 4,500 households in Tsukuba City, northeast of Tokyo, officials of relevant government section said.

    The earthquake with a magnitude of 6.7 struck at 1:45 a.m. (1645GMT, Wednesday). Its epicenter was about 40 kilometers below the surface of the sea in the Pacific off the coast of Ibaraki Prefecture, northeast of Tokyo, according to Japan Meteorological Agency (JMA).

    No tsunami warning was issued following the quake, which generated several minor aftershocks.

    The six people injured were in Tokyo, Ibaraki, Saitama and Chiba prefectures, Japanese media reported, adding that the quake could also be strongly felt in Tochigi Prefecture, north of Tokyo.

    The JMA said its early warning system, which bears much hope of Japanese people to reduce damage in major earthquakes, was about one minute behind preliminary tremors, and the agency will make efforts to improve the system.