A strong earthquake has hit central Japan, but there were no immediate reports of injuries or damage, and no tsunami warning was issued.

The Japan Meteorological Agency says the magnitude-6.8 earthquake hit parts of Nagano city and surrounding areas the hardest. The U.S. Geological Survey says the quake's magnitude was 6.2.

The earthquake struck at 10:08 p.m. Japan time on Saturday at a depth of 6 miles.

Japanese media reported that the Shinkansen bullet train service in the area was suspended after the earthquake.