PVMBG reported that seismic activity at Soputan rapidly and significantly increased at 1700 on 15 December.
An eruption began at 0102 on 16 December though dark and foggy conditions prevented views of emissions.
The event lasted for almost 10 minutes, and thunderous sounds were heard at the Soputan Volcano Observation Post located in Silian Raya (about 10 km SW).
The conditions improved about two hours later, and a dense ash plume was visible rising 3 km above the summit and drifting SE.
Incandescence from the summit was also visible.
An event that began at 0540 produced dense gray-to-black ash plumes that rose as high as 7 km above the summit and drifted SE.
The event lasted for 6 minutes and 10 seconds based on the seismic network.
Ash plumes from events at 0743 and 0857 rose as high as 7.5 km and drifted SW.
The Alert Level remained at 3 (on a scale of 1-4).
Residents and tourists were advised not to approach the craters within a radius of 4 km, or 6.5 km on the WSW flank.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)