The Yomiuri Shimbun An estimated magnitude-5.9 quake occurred in Osaka Prefecture at about 7: 58 a.m. Monday.
Meanwhile, Japan's JXTG Nippon Oil & Energy Corp says it has shut all refining units at its 115,000 barrels-per-day (bpd) Osaka refinery after the quake.
At least three people were killed - a 9-year-old girl and two men in their 80s - and more than 90 other people were hurt after a strong quake rattled the city of Osaka in western Japan on Monday morning, officials said.
A strong natural disaster has shaken the city of Osaka in western Japan.
Television images showed goods scattered on the floor of shops and building debris in streets.
At least 51 people were injured, mainly across the northern Osaka and neighboring prefectures, the broadcaster reports, citing data from local police and fire departments. Several others are reported in a state of "cardiopulmonary arrest", a condition usually used by Japanese authorities until a formal examination has been conducted to confirm death.
A strong quake knocked over walls and set off scattered fires around the city of Osaka in western Japan on Monday morning.
The epicenter of the quake was just north of Osaka city, said the Japan Meteorological Agency, which originally put the magnitude at 5.9 but later raised it to 6.1.
Japan Chief Cabinet Secretary Yoshihide Suga told reporters at a hastily convened press conference that there were no immediate reports of heavy damage, and that Prime Minister Shinzo Abe had ordered relevant ministries to gather information on the quake. As the quake was centred inland, there was no fear of a tsunami.
A number of train services were suspended, including the "shinkansen" bullet train. Bloomberg reported plants across the area were halted as firms assessed the damage.
Prime Minister Shinzo Abe told reporters the government was "working united, with its first priority on saving people's lives". In 1995, a magnitude 6.9 quake killed more than 6000 people when it struck in neighbouring Kobe.
Kansai Electric said on its website that around 170,000 homes in the Osaka region were without power.