The Japan Meteorological Agency says a volcanic eruption occurred early Monday morning on an island in the southwestern prefecture of Kagoshima.
The agency says the eruption took place on Suwanosejima Island at around 2:48 a.m.
The agency raised its volcanic alert level from 2 to 3 on its five-tier scale.
An agency official told a news conference that the eruption ejected large rocks up to 1.3 kilometers southeast of the Otake Crater.
A residential area on the island is located some 4 kilometers from the crater. Local officials say that as of December 1, the island had 81 residents.
The Meteorological Agency official warned about the possibility of large rocks falling on areas within about 2 kilometers of the crater.
He also called on people to take extra caution against volcanic ash and small rocks carried by winds.
Explosive eruptions have occurred on the island more frequently since December 21. Rocks from an eruption on Saturday were blown about 1 kilometer from the crater.