A very small eruption was observed at Mount Sakurajima early Wednesday, the Meteorological Agency said.
The eruption at 3:13 a.m. was the first observed at the 1,117-meter volcano overlooking the city of Kagoshima since the alert level was raised last week to 4 on a 5-point scale. An alert level of 4 warns residents nearby to prepare to evacuate, as a major eruption could be imminent.
The agency said it observed a phenomenon called volcanic glow, in which air above the crater looks red because of the reflection of magma and red-hot volcanic rocks, early in the day along with the latest eruption at the mountain's Showa vent.
Mount Sakurajima, in Kagoshima Prefecture, has had more than 1,000 eruptions since the start of this year, and the latest was one of the smallest, the agency said.