Papua New Guinea's volatile Ulawun volcano began spewing ash on Wednesday, prompting authorities to evacuate villages near the area.
The volcano on the remote Bismarck Archipelago chain is listed as one of 16 'Decade Volcanoes' targeted for research.
"The volcanic activity at Mt Ulawun began at 7:00 am this morning (local time) after slight rumbling and light emission," an official with the West New Britain Disaster Office observed.
"The Rabaul Volcano Observatory has declared a stage one alert warning of a possible eruption."
Witnesses reported ash spewing out of the summit, turning the sky dark.

GCC interior ministers hold emergency meeting in Riyadh
Gunshots fired in standoff at Philippine Senate over ICC suspect
Trump lands in China for Xi summit
Israeli airstrikes kill eight people on highway south of Beirut
Philippines' Senator says arrest imminent, urges public to block ICC transfer
UK's Starmer faces biggest challenge yet as resignation threat overshadows King's Speech
Israel steps up attacks on Gaza since Iran truce, as military says Hamas rearming
Trump says he does not need China's help to end Iran war
