The quake was detected around 18 kilometres (11 miles) off the Kyushu region around 9:19 pm (1219 GMT), according to the US Geological Survey.

The Japan Meteorological Agency (JMA) initially warned of possible tsunami waves of up to one metre (three feet) high and urged people to stay away from coastal waters.

However, several smaller tsunamis of only around 20 centimetres were detected at ports in the region, the weather agency said.

Live television feeds on Japanese television showed calm seas, as well as vessels operating normally and traffic running smoothly.

Only minor damage occurred, including a broken window at a train station and objects falling off shelves in a few stores, local media reported.

One man was slightly injured after falling over in his home, NHK reported.

- Megaquake -

The JMA warned in August that the likelihood of a "megaquake" was higher than normal after a magnitude 7.1 jolt that injured 15 people.

That was a particular kind of tremor known as a subduction megathrust quake, which has occurred in pairs in the past and can unleash massive tsunamis.

The advisory -- lifted after a week -- concerned the Nankai Trough, an 800-kilometre (500-mile) undersea gully parallel to Japan's Pacific coast.

The JMA said on Monday that the latest quake did not meet the criteria to trigger special warnings for the Nankai Trough again.

"However, it is important to keep in mind that an earthquake could occur at any time, and it is important to ensure that preparations for earthquakes are implemented on a daily basis," it said.

- Ring of Fire -

Japan sits on top of four major tectonic plates along the western edge of the Pacific "Ring of Fire" and is one of the world's most tectonically active countries.

The archipelago, home to around 125 million people, experiences around 1,500 jolts every year.

The vast majority are mild, although the damage they cause varies according to their location and depth below the Earth's surface.

A 7.5-magnitude quake struck the Noto peninsula on New Year's Day 2024, killing nearly 470 people in Japan's biggest jolt in more than a decade, many of them elderly residents in the aftermath.

Japan has strict construction regulations intended to ensure buildings can withstand strong earthquakes and routinely holds emergency drills to prepare for a major jolt.

But it is haunted by the memory of a massive 9.0-magnitude undersea quake off northeastern Japan in 2011, which triggered a tsunami that left around 18,500 people dead or missing.

The 2011 tsunami also sent three reactors into meltdown at the Fukushima nuclear plant, causing Japan's worst post-war disaster and the world's worst nuclear accident since Chernobyl.