Indonesia is bracing itself for more eruptions in the coming weeks as two volcanoes that erupted within hours of each other caused mass evacuations of people and flights to be rerouted.
Mount Sinabung in North Sumatra erupted at 7.04am on Monday, said National Disaster Management Agency spokesman Sutopo Purwo Nugroho. It has been erupting since mid-September this year, once every few days.
Hours before, at 4.05am, Mount Merapi in Central Java rumbled to life, spewing 2km of volcanic ash and causing a series of volcanic quakes.
"We have issued a notice of alert to airmen to avoid any flight routes through these areas as some of the ash clouds have risen to as high as 25,000 feet (about 7,600m)," said Transportation Ministry spokesman Bambang Ervan, who noted the thick volcanic ash could severely damage engines.
Indonesia sits on the Pacific Ring of Fire, a series of fault lines stretching from the Americas to Japan and South-east Asia, making it prone to earthquakes and volcanic activity.
The country also has some 130 active volcanoes across its sprawling archipelago.
On Monday, television images showed residents in villages in districts closest to the two volcanoes being evacuated by the authorities.
Some 5,000 who were returning home from shelters after fleeing their villages near Mount Sinabung, following the volcano's eruption on Sunday evening, were forced to turn back.
Volcanologist Surono, who goes by a single name, said the 2,600m mountain spat out up to 8,000m of volcanic ash on Monday morning, its highest in recent days. Sunday's eruption had sent ashes up 2,000m.
It had been dormant for three years before it started erupting again in September.
Over in Central Java, in addition to those already evacuated after the eruption of Mount Merapi, 600 families were asked to prepare for possible evacuation.
The volcano, one of the world's most active, saw one of its deadliest eruptions in 2010 that claimed 350 lives.
Officials on Monday warned that there could be more eruptions in the weeks to come because of seismic activity.
"We have noted increased seismic activities in Mount Sinabung," said Dr Sutopo.
"Residents are being told to stay calm and follow orders. Some have been traumatised by past eruptions and flooded shelters even though their villages are not in the danger zone."
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