Jakarta (Agencies) – Authorities in North Sulawesi shut an international airport and evacuated hundreds of people from the vicinity of the Ruang volcano after it belched explosive plumes of lava, rocks and ash for days, officials said on Thursday, declaring the highest alert on the situation.
Wednesday's dramatic eruption of the volcano on a remote island in North Sulawesi threw a fiery-red column of lava, incandescent rock and ash as much as three km (two miles) into the sky.
Purple flashes of lightning rent the sky above the erupting volcano, videos on social media showed.
"We're running, guys," said one witness who filmed the eruption while scrambling to evacuate. "We are escaping because the ash is coming close."
More than 800 people were evacuated from the area, with authorities widening the evacuation zone further after the volcanology agency raised the alert status.
"The potential for further eruption is still high, so we need to remain alert," agency official Heruningtyas Desi Purnamasari told reporters on Thursday, blaming a rapid escalation in volcanic activity.
The agency had also received reports that falling rocks and ash damaged homes and forced a nearby hospital to evacuate, the official said.
Transport authorities shut the airport in the provincial capital of Manado to protect against the showers of ash from the eruption.
Budget airline Air Asia cancelled flights with nine airports in East Malaysia and Brunei after aviation authorities warned of a safety threat.
The crater of Mount Ruang flamed with lava against a backdrop of lightning bolts overnight after erupting four times on Wednesday, forcing authorities to raise its alert level to the highest of a four-tiered system.
The volcano was still billowing a column of smoke on Thursday morning, prompting authorities to shut the Manado international airport for 24 hours.
Authorities said they were rushing to evacuate 11,000 residents from the nearby area that included the remote island of Tagulandang, home to around 20,000 people.
Some residents were already trying to flee in a panic, according to officials.
"Last night people evacuated on their own but without direction due to the volcano's eruption and materials in the form of small rocks that fell, so the people scattered to find evacuation routes," Jandry Paendong, an official from the local search and rescue agency, said in a statement Thursday.
He said 20 staff were helping evacuate residents along the coastline near the volcano on rubber boats.
He called for more boats and equipment so his team could "carry out evacuation for people in the coast or near the coast" facing the volcano.
Tourists and residents were warned to remain outside a six-kilometre exclusion zone.
More than 800 people were initially taken to safety from Ruang to nearby Tagulandang island after the first eruption on Tuesday evening before four more eruptions on Wednesday.
Officials have cordoned off an area of six kilometres (4 miles) around the volcano and are evacuating more residents, some from the neighbouring island of Tagulandang, said Abdul Muhari, spokesperson of the disaster mitigation agency.
About 1,500 of those in high-risk areas needed to be immediately evacuated, he added, while almost 12,000 more stand to be affected.
Officials have also flagged the risk of a tsunami if parts of the mountain collapse into the ocean below. About 400 people were killed in a tsunami unleashed by a previous eruption of the volcano in 1871.