Local news outlets say the quake was felt in the Saitama and Tokyo areas, with buildings swaying.
Metro operations were briefly suspended on all routes in Tokyo, but services restarted four minutes later.
An elevator maintenance firm in Tokyo said several elevators stopped in the metropolitan area due to the quake with commuters asked to “use emergency buttons,” according to NHK.
TASS news agency reports that books fell from shelves and furniture shook at its headquarters in Tokyo.
A 5.6 quake is considered strong according to the Japanese 7-point scale. NHK reports there was no immediate tsunami warning, however.
Japan Nuclear Power Association says a reactor at Tokai Nuclear Plant in Tokai village has "suspended operation" due to the quake. Tokyo Electric Power reports no incidents at the plant.
The Japanese meteorological society confirmed the reports of a 5.6 strong earthquake. It said the epicenter of the shocks was in the prefecture of Ibaraki.
No information of devastation or casualties has been reported from the Ibaraki prefecture.
Meanwhile, the US Geological Survey reports a 5.4 earthquake some 6 kilometers west of Iwai.