Authorities are warning it could erupt, and the area around Mount Agung has seen tremors and signs of magma rising to the surface in recent days.
Authorities have imposed a 12km (7.5-mile) exclusion zone around the mountain and issued their highest level alert on Friday.
The UK Foreign Office have updated their advice in the wake of a potential natural disaster.
Updating their travel advice on Friday 22 September, and confirming it is still current today, the FCO wrote: “The National Disaster Management Authority raised the volcanic alert level for Mount Agung in north east Bali to level 4.
“You should follow the advice of the local authorities and stay outside the exclusion zone which extends between 9 and 12 km from the crater.
“In the event of an eruption and volcanic ash clouds, which could cause flight disruptions, you should confirm your travel arrangements directly with your airline or travel agent before travelling to the airport.”
The main tourist areas of the island remain unaffected for now, and flights are still continuing to the region.
Indonesia’s national volcanology centre said in a statement (in Indonesian) on Sunday night that the mountain’s “seismic energy is increasing and has the potential to erupt”, the BBC reported.
A 200m-tall column of smoke was seen rising from the mountain early on Sunday, said the chief geologist monitoring the site, Gede Suantika.
He told the Reuters news agency: “We observed sulphuric smoke spewing from its crater and we never saw this before.”
Officials said they started detecting shallow tremors in late August, and first raised the alert from “normal” to the second-tier “vigilant” level on 14 September. Indonesia has a four-level volcano alert system.
Mount Agung, which is more than 3,000m above sea level, lies in the eastern part of Bali, which is a popular tourist destination.
The volcano is about 70km from the main tourist areas of Kuta and Seminyak, which remain unaffected for now.
Flights are continuing as normal at the moment, and the local tourism board said boats connecting to neighbouring islands Lombok and Java were also on schedule.
The board did advise visitors to “start preparing sufficient stock of face masks” in case of an eruption.
Volcanoes have been erupting around the world in recent weeks, with a disaster in Mexico claiming hundreds of lives.
