A strong earthquake with a preliminary magnitude of 6.2 on the Richter scale struck western Japan on Friday, the Japan Meteorological Agency said. No tsunami warning was issued for the 2.07 a.m. (1707 GMT Thursday) quake, the agency said. At least 17 people were injured from, according to public broadcaster NHK. There were no impacts on nuclear power plant in the region, according to the plant operator. The focus of the temblor was 78 km underground in Iyonada inland sea, the weather agency said. The quake registered upper 5 on the Japanese seismic intensity scale of 7 in Seiyo City in Ehime Prefecture, about 700km southwest of Tokyo. The weather agency defines an intensity of upper 5 as strong enough to make most dishes in a cupboard and most books on a bookshelf fall. At a press conference in Tokyo, a weather agency official warned that quakes measuring up to 4 in intensity could occur in areas around the epicenter in the coming week.