A 6.9-magnitude earthquake followed by a 7.1 tremor struck off southern Japan on Thursday, the United States Geological Survey said, with the local meteorological agency warning of tsunamis striking coastal areas.

Tsunamis of up to one metre were expected to arrive or have arrived in some coastal areas in Kyushu and Shikoku islands, broadcaster NHK reported.

"Tsunamis will strike repeatedly. Please do not enter the sea or approach the coast until the warning is lifted," the Japan Meteorological Agency said on X.

There were no immediate reports of any damage.

The USGS said that the first quake hit at 4:42pm at a depth of 33 kilometres, about 29km southeast of Miyazaki on Kyushu.

The second struck less than a minute later at a depth of 26 metres and was 20km northeast of Miyazaki.

The Japanese government set up a special task force in response to the quakes, according to a statement.

Sitting on top of four major tectonic plates along the western edge of the Pacific "Ring of Fire", Japan 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 and accounts for around 18% of the world's earthquakes.

On New Year's Day, at least 260 people died after a massive earthquake hit the peninsula, including 30 "quake-linked" deaths as well as those killed directly in the disaster.

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