Ash spewed as high as 2.1 km above the crater during one emission at 7:59 a.m. (2359 GMT, Dec. 7), within a radius of about 5 km around the mountain, the Indonesian Disaster Mitigation Agency said.
"Sometimes it is hard for the lava and magma to come out, and when there is pressure, it will spew ash," agency head Gede Suantika told Reuters.
Until the volcano started to enter the ash emission stage on Friday, its emissions since Nov. 25 had been mostly composed of steam, though there was some ash mixed in, he said.
The 9,800 ft Mount Agung volcano, which is capable of very violent eruptions, has shown a marked increase in activity in the last few weeks, stoking fears of a repeat of an eruption in 1963 that killed more than 1,000 people.
Authorities raised the alert status to the maximum after it started erupting last month, causing travel chaos by closing the island's airport for three days last week.
Operations were normal on Friday at the international airports in Bali and on nearby Lombok island.
(Reporting by Yuddy Cahya in KARANGASEM; Writing by Clarence Fernandez; Editing by Darren Schuettler)