Rumbling Mount Sinabung on the Indonesian island of Sumatra has shot billowing columns of ash more than 5,000 meters (16,400 feet) into the atmosphere and hot clouds down its slopes.
The National Disaster Mitigation Agency says there were no fatalities or injuries from Monday morning's eruption.
The volcano, one of three currently erupting in Indonesia, was dormant for four centuries before exploding in 2010, killing two people. Another eruption in 2014 killed 16 people, while seven died in a 2016 eruption.
Disaster agency spokesman Sutopo Purwo Nugroho says hot ash clouds traveled as far as 4,900 meters southward.
The regional volcanic ash advisory center in Darwin, Australia, issued a "red notice" to airlines.
Some 30,000 people have been forced to leave homes around the mountain in the past few years.