An earthquake with a preliminary magnitude of 6.9 struck southwestern Japan on Monday, with no injuries or damage reported at this time. A small tsunami was observed in parts of Miyazaki and Kochi prefectures, Kyodo reported.

Japan's meteorological agency said it was investigating whether the quake was linked to an increased risk of a “megathrust” in the Nankai Trench. The agency said the quake struck at 9:19 p.m. in Miyazaki, Shintomi and Takanabe in Miyazaki Prefecture with a magnitude of less than 5 on the Japanese seismic scale of 7. 

A tsunami about 20 centimeters high was observed in parts of Miyazaki Prefecture and 10 centimeters in parts of Kochi Prefecture, the agency said.

Some sections of the Kyushu Shinkansen high-speed train line were temporarily suspended due to the quake. 

The quake was also felt over a large area of western Japan.