The volcano, which has erupted at least 95 times since early this year, is currently on the highest alert level of Indonesia’s four-tiered system after authorities raised it earlier this month.
“A column of ash was observed, grey in colour with thick intensity, drifting westward,” Geology Agency head Muhammad Wafid said in a statement.
“Rumbling sounds were heard up to the (monitoring) post,” he added.
He called on the people not to go within an exclusion zone of between four and seven kilometres (2.5-4.3 miles) from the volcano’s crater.
The volcano erupted a few weeks ago on a similar scale, belching a huge ash tower five kilometres into the sky.
Ibu is one of Indonesia’s most active volcanoes, erupting more than 21,000 times last year.
Indonesia, a vast archipelago nation, experiences frequent seismic and volcanic activity due to its position on the Pacific “Ring of Fire”.
Last month, Mount Ruang in North Sulawesi province erupted more than half a dozen times, forcing thousands of residents of nearby islands to evacuate. It remains at the highest alert level.
All of the 800 or so residents of Ruang island will be permanently relocated.
By Agencies.