A strong earthquake with a preliminary magnitude of 6.1 jolted central and eastern Japan on Monday, the Japan Meteorological Agency said, but it did not issue a tsunami alert. The quake, which occurred at 11:58 p.m. (1458 GMT), was also felt in Tokyo. There were no immediate reports of injuries or damage. The focus of the tremor was 20 km (12 miles) below the surface of the earth, off the coast of Shizuoka prefecture, about 200 km west of Tokyo, Reuters quoted the Meteorological Agency as saying. All reactors at Chubu Electric Power's Hamaoka nuclear power plant in Shizuoka are shut after Prime Minister Naoto Kan called for its closure, citing research showing that the area is at particularly high risk for a major earthquake within the next few decades. No abnormalities have been reported from the Hamaoka plant, public broadcaster NHK reported, citing the Nuclear and Industrial Safety Agency.