Mount Sinabung volcano erupted Monday, sending a massive column of ash and smoke some 5,000 metres (16,400 feet)into the air, leaving local villages coated in debris and officials scrambling to hand out face masks to residents.
The volcano, on Sumatra island, which has been rumbling since 2010 and saw a deadly eruption in 2016, spewed the thick plume after activity picked up recent days.
"This was the biggest eruption for Sinabung this year," said volcanology agency chief Kasbani.
There were no reports of injuries or deaths.
No one lives inside a previously announced no-go zone around the volcano.
But hundreds of houses outside the seven-kilometre danger zone were covered in volcanic ash.
Officials have distributed face masks and urged local residents to stay indoors to avoid respiratory problems, said local disaster mitigation agency official Nata Nail Perangin-angin.
"In some villages the visibility was barely five metres after the eruption -- it was pitch black," Perangin-angin added.
Pressure inside the crater was threatening to spark collapses in its dome, the official said.
Sinabung roared back to life in 2010 for the first time in 400 years. After another period of inactivity it erupted once more in 2013, and has remained highly active since.
In 2016, seven people died in one of Sinabung's eruptions, while a 2014 eruption left 16 people dead.
Indonesia is home to around 130 volcanoes due to its position on the "Ring of Fire", a belt of tectonic plate boundaries circling the Pacific Ocean where frequent seismic activity occurs.