A magnitude 6.6 earthquake struck off Miyazaki Prefecture, southern Japan, on Monday evening local time. Tsunami reached parts of Miyazaki and Kochi prefectures. But a tsunami advisory issued for the two prefectures was lifted later on Monday night.

The magnitude 6.6 quake occurred in Hyuganada Sea, off the coast of Miyazaki Prefecture at 9:19 p.m., and in the hardest-hit areas had an intensity of lower 5 on the Japanese scale of 0 to 7. The focus is estimated to be 36 kilometers deep.

In Miyazaki City, a large window pane was broken at a railway station, and at a liquor store some bottles fell from shelves about 2 meters high.

Japan Meteorological Agency issued a tsunami advisory, but later lifted it. In Miyazaki, 20-centimeter tsunami were seen, while Kochi reported 10-centimeter tsunami.

The agency lifted the advisory at 11:50 p.m. on Monday. Japanese authorities are still urging people working in the sea to exercise caution.

The operator of the Sendai nuclear power plant in Kagoshima Prefecture says there have been no reports of abnormalities at the facility so far. It says radiation levels around the plant remain unchanged.

Some local trains in Miyazaki Prefecture have suspended operations since the quake took place. The Kyushu Shinkansen bullet train has been running at reduced speed between Kumamoto and Shin-yatsushiro.

An earthquake expert at Kyoto University says the tremor on Monday could have occurred where tectonic plates meet.

Assistant Professor Yamashita Yusuke of Kyoto University's Disaster Prevention Research Institute is well-versed in the mechanisms of the Nankai Trough. He has been analyzing seismic activity in Miyazaki Prefecture.

Yamashita said Monday's tremor took place at the edge of the area where a magnitude 7.1 quake struck in the Hyuganada Sea, off Miyazaki, in August of last year. He pointed out that the remaining cracked area could have moved.

Yamashita said the latest tremor will have little impact on a possible Nankai Trough mega-quake. He noted that the seismic energy released by Monday's quake is about half that of the one in August.

But he is urging caution against tremors on a similar scale for the time being, as the magnitude of the latest quake was close to seven.