Japan issued a tsunami advisory on Monday after a magnitude 6.7 earthquake struck the southwest of the country. The public warnings to stay away from coastal areas were later lifted.

The agency initially gave the magnitude estimate at 6.9, but later revised it down. There were no immediate reports of damage. Residents in some coastal areas were told to evacuate as a precautionary measure.

One man was slightly injured in Kyushu after falling down some stairs, NHK TV reported. Trains stopped running in Miyazaki Station, stranding passengers.

NHK said a tsunami, estimated to be as high as one metre, reached land within 30 minutes of the quake. The waters detected at Miyazaki Port measured 20 centimetres high, the reports said.

Tsunami advisories were issued for Miyazaki prefecture, where the quake was centred, in the southwestern island of Kyushu, as well as nearby Kochi prefecture in Shikoku island, shortly after the quake struck at 9:19 p.m. according to the agency. They were all called off shortly before midnight.

People were warned to stay away from the waters, including rivers. Agency official Shigeki Aoki told reporters that people should watch for landslides as well as falling objects in homes. Aftershocks are possible, especially in the next two or three days, he said.

The quake, centred at a depth of 30 kilometres, shook a wide area in Kyushu, the southwestern main island, Japans Meteorological Agency said.

NHK TV footage showed moving traffic and well-lit streets, meaning that electric power was still working. No problems were detected at the various monitoring posts for nuclear plants in the area.

Japan is frequently hit by earthquakes due to its location along the Ring of Fire, an arc of volcanoes and fault lines in the Pacific Basin.

Experts at the meteorological agency met late Monday to gauge how the latest temblor may be related to the so-called Nankai Trough quakes, but decided not to take any extraordinary measures for the time being. The term refers to a wide region believed to be prone to periodic major quakes.

A Nankai Trough quake off Shikoku in 1946 killed more than 1,300 people. The area was hit by a 7.1 magnitude quake in August last year.