A series of six earthquakes registering up to 5.5 on the Richter scale shook central Japan on Friday. There were no immediate reports of damage or casualties.

The first quake was reported in the Nagano and Takada areas, about 110 miles northwest of Tokyo, and around Niigata, about 160 miles northwest of the capital, the Meteorological Agency said.Five more temblors were reported within two hours in the general area. The agency said the earthquakes' epicenter was at a depth of less than three miles in western Niigata Prefecture.