A volcano on Japan's major western island of Kyushu, called Sakurajima, erupted at about 8.05pm on Sunday, the Japanese Meteorological Agency (JMA) said, but media said there were no immediate reports of damage.

There were reports of volcanic stones raining down at a distance of 2.5 km from the volcano, NHK public television said. The eruption alert level has been raised to 5, the highest, with some areas advised to evacuate, it added.

Japan's nuclear regulators said no irregularities had been detected at the nearby Sendai nuclear power plant.

Sakurajima is one of Japan's most active volcanoes and eruptions of varying levels take place on a regular basis. In 2019 it spewed ash 5.5 km high.

Video footage from Sunday's eruption showed what appeared to be a red mass flowing down one side of the volcano, with red projectiles shooting out while smoke, hard to see in the darkness, billowed up.

Most of the city of Kagoshima is across the bay from the volcano but several residential areas within about 3 km of the crater may be ordered to evacuate, NHK said.

Officials at Prime Minister Fumio Kishida's office were gathering information about the situation, it added. (Reuters)