The 2,963-meter (9,721-foot) high Merapi is one of Indonesia’s most active volcanoes and is already at the country’s second highest warning level.
Kasbani, the head of Indonesia’s volcanology and geological risk reduction center, said Merapi had spewed out “rather intense” hot clouds at least 30 times since Wednesday morning, warning of the danger of lava cutting roads near the volcano.
Photos shared on social media showed as if on the homes of some residents in the area.
There were no immediate reports of damage, but some residents chose to leave their homes, the local disaster mitigation agency said.
Indonesia, located on the so-called “Ring of Fire”, has more volcanoes than any other country and Merapi erupted violently in 2010, killing more than 350 people.
The eruption comes weeks after a 6.2 magnitude earthquake shook the Indonesian island of Sulawesi and killed dozens of people.