The undersea volcano East Epi in Vanuatu in the Pacific erupted on Wednesday, throwing ash up to 100 meters high.
Authorities advised ships and planes to avoid the area.
“We ask local people to be wary of potential powerful explosions as the eruptions are still ongoing,” Ricardo William, a volcano specialist with the Vanuatu Department of Meteorology and Geological Hazards, told AFP.
A safety perimeter of 10 km has been established around the underwater volcano, which is 68 km north of Port Vila, the capital of the Pacific state.
Steam had been reported over the site then the volcano had started throwing ash Wednesday morning.
According to the local meteorology department, volcanic activity began just before 8 a.m. local time (2100 GMT Tuesday).
Government official Philip Dick told AFP the ground had started to tremble and smoke could be seen over the site in the early hours of the morning.
“Then the explosions started – there is still a bad smell of sulfur in the surrounding villages,” he added.
Authorities upgraded the volcano alert to the first level (out of five), indicating “minor civil unrest.”
Residents of the nearby islands of Epi and Tongoa have been ordered to avoid the coast.
The ministry said in a statement that although the Alaska Tsunami Warning Center has not detected any activity in the Vanuatu region, “such eruptions have the potential to generate tsunami waves.”
Vanuatu is located in an area of high seismic activity, dubbed the “Pacific Ring of Fire,” where tectonic plates meet.