The 2,963 meter (9,721 feet) high Merapi is one of Indonesia’s most active volcanoes and is already on the country’s second highest alert level.
Kasbani, the head of Indonesia’s volcanology and geological hazard mitigation center, said Merapi had spewed “quite intense” hot clouds at least 30 times since Wednesday morning and warned of a danger of lava cutting roads near the volcano.
Photographs shared on social media showed ash covering the homes of some nearby residents.
There were no immediate reports of damage, but some residents had chosen to leave their homes, said the local disaster mitigation agency.
Located on the so-called “Ring of Fire,” Indonesia has more volcanoes than any other country and Merapi violently erupted in 2010, killing more than 350 people.
The eruption comes just weeks after a 6.2-magnitude earthquake on Indonesia’s Sulawesi island flattened buildings and left dozens dead.