TOKYO (Reuters) - A strong earthquake with a preliminary magnitude of 5.5 jolted eastern Japan on Saturday morning, but there were no immediate reports of injury or damage and no tsunami warning was issued.
The focus of the tremor was 20 km (12 miles) below the surface of the earth, in Yamanashi prefecture, west of Tokyo, the Japan Meteorological Agency said.
The quake, at 7:43 a.m., was also felt in the capital.
Earthquakes are common in Japan, one of the world's most seismically active areas. The country accounts for about 20 percent of the world's earthquakes of magnitude 6 or greater.
On March 11, 2011, the northeast coast was struck by a magnitude 9 earthquake, the strongest quake in Japan on record, and a massive tsunami, which triggered the world's worst nuclear crisis in 25 years since Chernobyl. The disaster left up to 23,000 dead or missing.
(Reporting by Chris Gallagher, editing by Matthew Lewis)