The volcano agency's chief Kasbani said Mount Agung had a history of major eruptions that eclipsed recent episodes in Indonesia, including the 2010 eruption of Mount Merapi in Central Java that claimed at least 350 lives.
"The chance that an eruption will happen is quite big".
Another disaster agency official, Waskita Sutadewa in Bali, said people have scattered to all corners of the island and some have crossed to the neighboring island of Lombok.
In a statement on its website it said an increase in the frequency of the tremors indicated magma was moving towards the surface, and that the "number of quake events is greater than ever".
The latest data shows that Mount Agung experienced 844 volcanic earthquakes on Monday, and between 300 and 400 earthquakes by midday on Tuesday.
Evacuees have packed into temporary shelters or moved in with relatives.
More than 15,000 people of Bali around the foot of Mount Agung, a volcano were were evacuated to GOR Swacepura refuge and 125 other places on September 23.
Balinese residents, worldwide NGOs and the government have begun organising aid.
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Around 62,000 people lived in the danger zone before the evacuations, according to the agency, but residents just outside the area have also left as a precaution.
I Ketut Subandi, head of logistics at the village of Tana Ampo, said basic food items like rice, instant noodles, cooking oil and water were most needed.
He said the aid package included 5,000 blankets, 18,230 mattresses, 520,000 masks and 12,000 kilograms of rice.
The central government has set aside a relief fund of almost $150 million in case of an eruption.
"Instrumentally we have never recorded such high energy or seismicity from Mount Agung", Devy Kamil Syahbana, a seismologist from Indonesia's volcanology centre, told the Guardian.
Hundreds of domestic and worldwide flights were disrupted in 2016 when a volcano erupted on Bali's neighbouring Lombok island, sending up columns of ash and debris.
Indonesia has about 120 active volcanoes.