A powerful earthquake with an estimated magnitude of 6.8 rocked northwestern Japan on June 18, prompting tsunami warnings for some coastal areas along the Sea of Japan.

The temblor registered an upper 6 on the Japanese seismic scale of 7 in Murakami, Niigata Prefecture.

The earthquake struck at 10:22 p.m. with its focus about 10 kilometers deep off the western coast of Yamagata Prefecture.

The Japan Meteorological Agency issued tsunami warnings for coastal areas of Yamagata Prefecture, Niigata Prefecture, Sado Island and the Noto region of Ishikawa Prefecture.

It said the maximum tsunami height is expected to be about 1 meter.

Tohoku Electric Power Co. said the earthquake caused power outages in some areas in Yamagata and Niigata prefectures.

Services on the Joetsu, Tohoku and Hokuriku Shinkansen lines were partially or entirely suspended, according to East Japan Railway Co.

No abnormalities were reported at Tokyo Electric Power Co.’s Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture, which had been offine, according to the Nuclear Regulation Authority.