A strong earthquake hit off the eastern coast of central Japan on Sunday, rattling buildings across a broad swath of the country, including Tokyo.
There were no immediate reports of damage or casualties, and the government said there was no danger from tsunamis.
Japan's early warning system predicted the earthquake just before it hit, with public broadcaster NHK interrupting a sumo match to warn residents to take cover.
The quake had an initial estimated magnitude of 6.6, according to the Japan Meteorological Agency. It hit at 5:08 p.m. local time.
The earthquake was centered about 50 miles off the eastern coast of central Fukushima Prefecture, and struck at a depth of 25 miles.
It was strong enough to gently sway buildings in Tokyo, about 185 miles to the southwest, for several seconds.
Television images from the regions near where the quake was centered showed no damage, with cars driving normally.
Some train services in the region, including the Shinkansen bullet trains, were stopped following the quake, AFP reported.
The Tohoku Electric Power Co's Onagawa nuclear power plants were operating normally after the quake, an official told Reuters.
The country is one of the world's most earthquake-prone countries. In 1995, a magnitude-7.2 quake in the western port city of Kobe killed 6,400 people.