A strong earthquake jolted Tokyo early on Monday, rattling windows and nerves, although there were no initial reports of major damage.
The national broadcaster NHK, citing local authorities, said 17 people were reported injured, some of them from falls as the quake struck.
The Japan Meteorological Agency said the quake at 5.18am local time (20h18 GMT on Sunday) had a magnitude of 6.0 and was centred 160km under the seabed near Izu Oshima island south of Tokyo.
The quake was felt across a wide area of Japan, with the strongest shaking registered in central Tokyo, the agency reported.
The Tokyo Fire Department reported that four people were injured, but details were not immediately available.
The national broadcaster NHK said it was the strongest quake felt in the Japanese capital since the aftershocks of a magnitude-9 earthquake and tsunami in March 2011 off the north-eastern coast that left more than 18 500 people dead or missing.
There were no reports of damage or other abnormalities from the Fukushima Dai-Ichi nuclear plant, which was crippled in the 2011 disasters, leading to the closures of all Japan's nuclear reactors for safety checks.
NHK reported some delays in train services on Monday and said speed restrictions were imposed briefly on expressways in the affected area as a precaution. - Sapa-AP