TOKYO A strong earthquake with a preliminary magnitude of 6.4 jolted northeast Japan on Sunday, the Japan Meteorological Agency said. The quake, at 3:54 a.m. (1854 GMT Saturday), was also felt in Tokyo.
There were no immediate reports of injuries or damage, and no tsunami warning was issued.
The focus of the quake was off the coast of Fukushima prefecture. There were no abnormalities at the Fukushima Daiichi nuclear plant, the operator Tokyo Electric Power Co said.
A 9.0 magnitude quake and tsunami on March 11 knocked out the Fukushima plant's reactor cooling systems, triggering a radiation crisis.
Police in Fukushima and neighbouring Miyagi prefecture said they had received no reports of damage or injuries
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.
The March 11 earthquake, the strongest in Japan on record, and a massive tsunami triggered the world's worst nuclear crisis in 25 years, since Chernobyl. The disaster left up to 23,000 dead or missing.