Up to 50,000 residents flee from Bali volcano amid fears it is about to erupt

Up to 50,000 people have fled the largest volcano on the Indonesian island of Bali, fearing it will erupt at any moment.

A natural disaster has been declared in parts of Bali as authorities imposed an exclusion zone around Mount Agung following increasing volcanic activity on Sunday, the Daily Mail reported.

Strong tremors rippled through areas in the eastern part of the one of the world's most popular tourist destinations, packed with Australian families enjoying the school holidays, sparking authorities to order people to leave a 12km zone around the mountain.

Villagers rest at a temporary shelter in Klungkung, Bali, Indonesia. Photo / AP

The numbers from disaster officials on Sunday are more than double previous estimates and are continuing to rise, they say.

It includes people who left voluntarily as well as those told to evacuate from the exclusion zone as increasing tremors rattle the region.

Authorities raised the volcano's alert status to the highest level on Friday following a "tremendous increase" in seismic activity. Its last eruption in 1963 killed 1100 people.

Luhut Binsar Panjaitan, a senior Cabinet minister, said Sunday that the districts surrounding the volcano "must be prepared for the worst".

The National Disaster Mitigation Agency has praised the welcoming response of local communities on Bali to the flood of evacuees.

The agency has sent food and logistical supplies to the area, while also calling for public donations.

Thousands are living in temporary shelters, sport centers, village halls and with relatives or friends. Some return to the danger zone during the day to tend to livestock.

National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said 14 tonnes of aid has been sent, including tents, blankets, mattresses and portable communications equipment.

A family rest in a tent at an evacuee camp in Klungkung. Photo / AP

Truck driver Wayan Suparta said he and his family left their village 5km from the mountain several days ago, bringing just clothes and blankets to a temporary camp in Rendang.

The 35-year-old said he sold the family's cow because they don't know when they'll be able to return.

Officials have said there is no current danger to people in other parts of Bali, a popular tourist island famous for its surfing, beaches and elegant Hindu culture.

Hoaxes have proliferated online, with videos of previous eruptions in Indonesia circulated as current events at Mount Agung.

Officials urged the public to remain calm amid false reports and videos circulating online of an eruption.

"The latest analysis indicates that Mount Agung's seismic energy is increasing and has the potential to erupt," the National Vulcanology Center said in a statement.

"However, no one can predict exactly when there will be an eruption," it added.

Flights at Bali's international airport were operating normally on Sunday as were tourist spots across the rest of the island.

Meanwhile, Australian flights to Bali continued as scheduled on Sunday.

Virgin Australia, Jetstar and Qantas flights to Denpasar International Airport remained unaffected but the airlines said they were monitoring warnings.

Virgin Australia warned of possible flight delays and said some Bali bound flights would be making fuel stops in Darwin as a precautionary measure.

"This ensures that if an eruption occurs while the aircraft is en route, we will be able to get guests back to their originating port safely and quickly," the airline said in a statement.

A man observes a map of the Mount Agung volcano at the Mount Agung monitoring station in Bali. Photo / AP

All Jetstar flights were operating as scheduled and passengers would be notified individually if changes occurred, the company said in a statement on Sunday.

"Our pilots and meteorologists will continue to monitor the latest information from the Volcanic Ash Advisory Centre," the statement said.

Qantas flights were also operating as scheduled, a spokeswoman told AAP on Sunday.

The government's Smart Traveller website urges visitors to monitor local media reports and follow instructions of local authorities.

Australians are also advised to exercise a high degree of caution in Indonesia and to contact their tour operators to confirm travel plans.

In 1963, the 3031m Agung hurled ash as high as 20km, according to volcanologists, and remained active for about a year.

Lava traveled 7.5km and ash reached Indonesia's capital, Jakarta, about 1000km away.

The mountain, 72km to the northeast of the tourist hotspot of Kuta, is among more than 120 active volcanoes in Indonesia.

The country of thousands of islands is prone to seismic upheaval due to its location on the Pacific 'Ring of Fire,' an arc of volcanoes and fault lines encircling the Pacific Basin.