Sinabung was seen spewing lava and blasting plumes of ash 2.5km into the air, amid growing fears that Mount Agung could be next to erupt.
The terrifying photos were taken from Sukendi village in Karo, North Sumatera and will be an ominous sign for the people of Bali.
Locals living near Sinabung have been warned to stay at least 7km away from the volcano, after 10 people were killed by an eruption earlier this year.
Meanwhile, more than 140,000 people have evacuated their homes in Bali to escape the possible eruption of Mount Agung.
Increased seismic activity in recent weeks has seen the volcano alert raised to level 4, meaning an eruption is imminent.
More than 220 earthquakes were recorded around Agung overnight, but volcanologists still cannot accurately predict whether or not the volcano will blow.
The latest MAGMA Indonesia statement said: “Based on the analysis of current monitoring data, at this moment, the probability of an eruption is higher than the probability of no eruption.
“However, the probability may change at any time depending on current monitoring data.
“If an eruption does occur, it is most likely to be small at first; however, a large eruption may follow. The size of future eruptions cannot be determined with certainty.
“The exact date and time of future eruptions cannot be predicted, however; CVGHM will issue warnings when conditions change and eruptions are more certain.”
Cracks have been detected along the crater of Mount Agung over the past week and white steam containing sulphurous fumes has been observed rising up to 200m above the summit.
Despite the looming threat of an eruption, the Balinese Government insist the island is safe for travel.
Bali’s tourism chief AA Gede Yuniartha Putra said: “Bali tourism is safe. Do not spread the misleading news that Bali is not safe because Mount Agung is on the highest alert status. Please, come and visit Bali.”
Agung and Sinabung both sit on the deadly Pacific Ring of Fire in Indonesia, which is the most active volcano belt on the planet.