Up to 35,000 people have fled a looming volcanic eruption on the island of Bali after some 300 tremors, increasing in both frequency and intensity, registered between midnight and 6am Sunday.

The Indonesian National Disaster Mitigation Agency has set up temporary shelters for evacuees and provided 14 tons of aid including food, water, tents, blankets and mattresses.

“Four days after we raised the alert level to level three, there were extraordinary tremors ... the biggest since 1963. So, we raised the alert level to level four,” the head of the Center for Volcanology and Geological Hazard Mitigation (PVMBG), Kasbani, told News.com.au.

“We could not predict when the mountain will erupt,” he added. “However, we don’t know whether the eruption now will be bigger or smaller. If we see the eruption in 1963, it could take one year.”

The eruption alert was raised to the highest level on Friday following a "tremendous increase" in seismic activity. For context, from midnight to noon on Friday, a total of 198 tremors were recorded compared with the 300 that took place in the six-hour period overnight Sunday.

READ MORE: Thousands evacuated as Bali volcano spews ominous smoke 3,000 meters high

There is no immediate threat to residents outside the 12km radius of the safety cordon around Mount Agung, but if it were to erupt, it would be the volcano’s first eruption in half a century.

The 1963 eruption killed 1,100 people with the ash cloud reaching an altitude of 20km (12 miles) and the lava flow extending 7.5km (4.7 miles) from the volcano, reports ABC News.

READ MORE: Volcanic ash cloud sparks ‘doomsday’ scenes on Indonesian island (PHOTOS, VIDEOS)

The current exclusion zone was extended from 6km to 12km based on lava flows from the 1963 eruption.

“We have prepared 500,000 masks to anticipate volcanic ash which is very important, because the ash is very dangerous,” the National Disaster Mitigation Agency (BNPB) head, Willem Rampangilei, told News.com.au.

“This is a very complex work. We should work hard to minimize victims. We keep hoping that the eruption will not happen. However, we should be ready for the best scenario if the eruption does happen,” he added. “We have declared that we are in emergency response period for next one month. I hope the eruption will not happen.”

The BNPB has also warned about a series of hoaxes which spread on social media and exacerbated an already stressful situation for worried Indonesians.