TOKYO, July 20 (Xinhua) -- An earthquake with a preliminary magnitude of 5.6 struck off the coast of Fukushima Prefecture in the northern Tohoku region on Japan's main island of Honshu on Thursday, although no tsunami warning has been issued.

According to the Japan Meteorological Agency (JMA), the temblor occurred at 9:11 a.m. local time (0011 GMT), at a latitude of 37.3 degrees north and a longitude of 141.6 degrees east.

The quake occurred at a depth of 40 km in the Pacific Ocean, the weather agency said, and was felt across wide swathes of the Tohoku region and eastern Japan.

The quake registered 4 on the Japanese seismic scale which peaks at 7, in Iwaki, a city located in the southern part of the Hamadori coastal region of Fukushima Prefecture, as well as registering 4 in Ishinomaki, a city located in Miyagi Prefecture in the Tohoku region, the JMA said.

The quake registered 3 in some parts of Iwate, in Tohoku and in Ibaraki Prefecture, which lies in the Kanto region of Japan.

The weather agency also said the offshore quake registered 2 on Japan's seismic scale in the nation's capital city of Tokyo, where buildings were shaken briefly.

The JMA has not issued a tsunami alert as a result of the quake and no abnormalities have been observed at the crippled Fukushima Daiichi nuclear power plant as a result of the temblor, its operator said.