A spectacular volcanic eruption in Indonesia has killed at least two people and forced mass evacuations, disrupting long-haul flights and closing international airports Friday.

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.

TV images showed ash and rocks raining down on nearby villages, while AFP correspondents at the scene saw terrified locals covered in ash fleeing in cars and on motorbikes towards evacuation centres.

A man and a woman, both in their 60s, were crushed to death after volcanic material blanketed rooftops, causing their separate homes in the sub-district of Malang to cave in, National Disaster Mitigation Agency Spokesman Sutopo Purwo Nugroho said.

"The homes were poorly built and seemed to have collapsed easily under the weight," he said.

Some 200,000 people in a 10-kilometre (six-mile) radius from the volcano were ordered to evacuate, according to national disaster officials, though many tried to return to their homes to gather clothing and valuables -- only to be forced back by a continuous downpour of volcanic materials.

"A rain of ash, sand and rocks is reaching up to 15 kilometres (nine miles)" from the volcano's crater, Nugroho said.

Virgin Australia said it had cancelled all its flights to and from Phuket, Denpasar, Christmas Island and Cocos Island on Friday, saying in a statement that "the safety of our customers is the highest priority" and that the airline would keep monitoring the plume.

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.

"We will have to call them this afternoon for rescheduling, but I doubt we will be travelling soon," she said.

A spokeswoman for Australian airline Qantas said that Friday flights between Jakarta and Sydney had been pushed back to Saturday.

"Flight paths from Australia to Singapore have been altered as a result of the volcanic ash cloud in Java," she said.

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 told AFP, while Metro TV showed images of grounded planes covered in ash.

"All flights to those airports have been cancelled, and other flights, including some between Australia and Indonesia, have been rerouted," Bakti said.

"We will reassess the situation tonight regarding reopening the airports, but at the moment, it's too dangerous to fly anywhere near the plume."

On the outskirts of Yogyakarta, authorities closed Borobudur -- the world's largest Buddhist temple, which attracts hundred of tourists daily -- after it was also rained upon with dust from the volcano some 200 kilometres east.

At a temporary shelter in the village of Bladak, roughly 10 kilometres from the volcano's crater, around 400 displaced people, including children, slept 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 around the volcano could still be felt Friday as volcanic materials continued to blanket the rooftops of entire villages.

Communities within the affected 15-kilometre radius began clearing piles of grey ash as high as five centimetres from roads, Nugroho said.

The National Search and Rescue Agency warned residents not to return home as lava was still flowing through some villages, while sulphur was lingering in the air in others.

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 1568 eruption.

It is one of some 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 people dead and has been erupting on an almost daily basis since September.