Mount Kelud, considered one of the most dangerous volcanoes on the main island of Java, spewed red-hot ash and rocks high into the air late Thursday night just hours after its alert status was raised.
Villagers in eastern Java described the terror of volcanic materials raining down on their homes, while AFP correspondents at the scene saw residents covered in grey dust fleeing in cars and on motorbikes towards evacuation centres.
Sunar, a 60-year-old from a village eight kilometres (five miles) in Blitar district, said his home also collapsed after being hit with "rocks the size of fists".
"The whole place was shaking -- it was like we were on a ship in high seas. We fled and could see lava in the distance flowing into a river," said Sunar, who goes by one name.
A man and a woman, both in their 60s, were crushed to death after volcanic material that had blanketed rooftops caused their homes in the sub-district of Malang to cave in, National Disaster Mitigation Agency Spokesman Sutopo Purwo Nugroho said.
Dian Julihadi, 32, from Blitar district, said: "It was like fireworks. There was a loud bang and bright red lights shot up into the air."
Nugroho confirmed the materials were still raining down on villages within a radius of 15 kilometres from the volcano on Friday, but said that some activities were resuming "as normal".
Some 200,000 people were ordered to evacuate, though some families have ignored the orders and just over 100,000 are now in temporary shelters, Nugroho said.
Several people tried to return home to gather clothing and valuables -- only to be forced back by the continuous downpour of volcanic materials.
"Too dangerous to fly"The ash has blanketed the Javanese cities of Surabaya, Yogyakarta and Solo, where international airports have been closed temporarily, Transport Ministry director general of aviation Herry Bakti said, while grounded planes were seen covered in the dust.
"All flights to those airports have been cancelled, and other flights, including some between Australia and Indonesia, have been rerouted," Bakti said, adding it was too dangerous to fly near the plume.
In Singapore, Changi Airport advises passengers travelling to Semarang, Solo, Surabaya and Yogyakarta to check with their respective airlines on their flight's status before going to the airport.
Virgin Australia said in a statement it had cancelled all its flights to and from Phuket, Bali, Christmas Island and Cocos Island on Friday, adding that "the safety of our customers is the highest priority" and that the airline would keep monitoring conditions.
Australian nurse Susanne Webster, 38, was on a late-morning Virgin flight from Sydney to Bali that was turned around.
"About two hours in, the pilot announced over in Indonesia there was a volcano that erupted and that we were turning the plane back," she told AFP, adding they were still in Australian airspace at the time.
Australian airline Qantas postponed Friday flights between Jakarta and Sydney to Saturday, while Singapore Airlines cancelled its flights to Surabaya, a popular destination for golfing tourists.
AirAsia cancelled flights to several Javanese cities, with 21 flights affected in total, including three between Indonesian and Malaysia.
"The ashes could... compromise the safety and performance of the aircraft, such as (cause) permanent damage to the engine," AirAsia said in a statement, adding visibility was also a concern.
On the outskirts of Yogyakarta, authorities closed Borobudur -- the world's largest Buddhist temple, which attracts hundreds of tourists daily -- after it was rained upon with dust from the volcano about 200 kilometres to the east.
Around 400 people remained at a temporary shelter in the village of Bladak, roughly 10 kilometres from the volcano's crater, after spending the night on the floor wearing safety masks.
The Center for Volcanology and Geological Hazard Mitigation said there was little chance of another eruption as powerful as Thursday night's, but tremors could still be felt Friday as communities began clearing piles of ash up to five centimetres high on roads.
The 1,731-metre (5,712-foot) Mount Kelud has claimed more than 15,000 lives since 1500, including around 10,000 deaths in a massive eruption in 1568.
It is one of 130 active volcanoes in Indonesia, which sits on the Pacific Ring of Fire, a belt of seismic activity running around the basin of the Pacific Ocean.
Earlier this month another volcano, Mount Sinabung on western Sumatra island unleashed an enormous eruption that left at least 16 dead and has been erupting almost daily since September. (ChannelNewsAsia)