The airport on the holiday island of Bali has reopened after tens of thousands of travellers were stranded for two days due to an erupting volcano, but Indonesia's President said the danger has not passed and urged anyone within the mountain's exclusion zone to get out "for the sake of their safety."

Mount Agung has been hurling clouds of white and dark gray ash about 7,600m (4.7 miles) into the atmosphere and lava is welling up in the crater, though it remains unclear how bad the current situation might get or how long it could last.

Indonesian authorities raised their warning for the volcano to the top level four alert earlier in the week, and told residents around the mountain to immediately evacuate, warning of an "imminent" risk of a larger eruption.

Bali's Mount Agung volcano eruption: in pictures Show all 22 1 /22 Bali's Mount Agung volcano eruption: in pictures Bali's Mount Agung volcano eruption: in pictures A fisherman drives a traditional boat as Mount Agung erupts AFP/Getty Bali's Mount Agung volcano eruption: in pictures Police evacuate a villager from inside the exclusion zone REUTERS Bali's Mount Agung volcano eruption: in pictures Villagers watch a river overflowing with water mixed with volcanic ash REUTERS Bali's Mount Agung volcano eruption: in pictures A flight information board shows cancelled flights at Ngurah Rai International Airport in Denpasar, Bali AP Bali's Mount Agung volcano eruption: in pictures A villager takes his cows to a field with Mount Agung volcano erupting in the background AP Bali's Mount Agung volcano eruption: in pictures Police officers wear masks as they patrol in a village in Karangasem AP Bali's Mount Agung volcano eruption: in pictures Clouds of ashes rise from the Mount Agung volcano AP Bali's Mount Agung volcano eruption: in pictures Passengers talk to airline workers as their flights are cancelled AP Bali's Mount Agung volcano eruption: in pictures Mount Agung AP Bali's Mount Agung volcano eruption: in pictures A boy takes pictures during Mount Agung's eruption AFP/Getty Images Bali's Mount Agung volcano eruption: in pictures Mount Agung volcano is seen spewing smoke and ash in Bali EMILIO KUZMA-FLOYD/via REUTERS Bali's Mount Agung volcano eruption: in pictures Balinese Hindus take part in a ceremony, where they pray near Mount Agung in hope of preventing a volcanic eruption AFP/Getty Images Bali's Mount Agung volcano eruption: in pictures Mount Agung volcano erupts for a second time in less than a week REUTERS Bali's Mount Agung volcano eruption: in pictures Balinese Hindus take part in a ceremony AFP/Getty Images Bali's Mount Agung volcano eruption: in pictures Mount Agung volcano is seen erupting from Glumpang village REUTERS Bali's Mount Agung volcano eruption: in pictures A Balinese farmer works as Mount Agung volcano spews volcanic ash EPA Bali's Mount Agung volcano eruption: in pictures Mount Agung during an eruption seen from Kubu sub-district in Karangasem Regency AFP Bali's Mount Agung volcano eruption: in pictures A villager walks near a rice field following the eruption of Mount Agung AP Bali's Mount Agung volcano eruption: in pictures Mount Agung volcano spews volcanic ash Rex Features Bali's Mount Agung volcano eruption: in pictures An officer with the disaster management agency BPBD places a mask on child at a shelter for residents sheltering from Mount Agung volcano Antara Foto/Nyoman Budhiana/ via REUTERS Bali's Mount Agung volcano eruption: in pictures Mount Agung volcano erupts REUTERS Bali's Mount Agung volcano eruption: in pictures Mount Agung's eruption is seen between Balinese temple at Kubu AFP/Getty Images

Airport spokesman Arie Ahsannurohim said the volcanic ash has drifted south and southeast, leaving clean space above the airport for planes to land and take off.

It has been closed since Monday morning, disrupting travel for tens of thousands of people.

The closure of the airport had stranded tens of thousands of travellers, affecting tourists already on Bali and people who were ready to fly to the island from abroad or within Indonesia.

President Joko "Jokowi" Widodo ordered all concerned ministries and agencies, as well as the military and police, to help Bali's government deal with the disaster.

"I hope there will be no victims hit by the eruption," he said.

Authorities have told 100,000 people to leave homes nearest the volcano, though tens of thousands stayed because they felt safe or didn't want to abandon livestock.

Nearly 40,000 people are now staying in 225 shelters, according to the Disaster Mitigation Agency in Karangasem.

Mudflows have been seen on the mountain's slopes, and authorities warned more are possible, since it's the rainy season in Bali.

Mount Agung's last major eruption in 1963 killed about 1,100 people.

Indonesia sits on the "Pacific Ring of Fire" and has more than 120 active volcanoes.