Indonesia has raised the alert status of Anak Krakatau volcano to Level III, the second-highest level in its four-tier warning system, after the volcano recorded at least 13 eruptions on Friday.
The Geological Agency announced that the alert level was raised from Level II at 9pm local time on October 9, following an assessment of volcanic activity since the beginning of the month.
“Signs of increased activity on a low scale began to emerge in early October 2026,” the agency said in an assessment dated October 9. However, seismic monitoring had not detected a significant overall increase in volcanic earthquakes.
Located in the Sunda Strait between Java and Sumatra, Anak Krakatau had been downgraded to Level II on September 21 after activity declined. It had remained at Level III since early September before the downgrade.
The latest developments follow a series of major eruptions in early September that sent volcanic ash into the atmosphere and forced temporary airport closures. The disruption affected approximately 341,000 passengers and 2,961 flights.
According to eruption reports published by the Volcanology and Geological Hazard Mitigation Centre (PVMBG), the first two documented eruptions on Friday occurred at 4.17pm and 4.30pm, producing ash columns that rose 250 metres and 150 metres above the summit respectively.
Another 11 eruptions were recorded between 6.28pm and 9.20pm, although their ash columns could not be observed. Full-day seismic monitoring recorded 26 eruption-related earthquakes.
Including four eruptions recorded on October 5 and another on October 8, Anak Krakatau has registered at least 18 documented eruptions since the beginning of October.
The Geological Agency also reported that satellite monitoring detected sulphur dioxide emissions ranging from 71 to 237.5 tonnes per day between September 21 and October 9. Incandescence, or visible glowing from the volcano, has also been observed since October 6.
Meanwhile, Australia’s Darwin Volcanic Ash Advisory Centre reported that volcanic ash reached an altitude of approximately 1.8 kilometres above sea level at 10.50pm on Friday. The ash drifted westward across the Sunda Strait towards the Indian Ocean at around nine kilometres per hour and was forecast to dissipate within six to 12 hours.
Authorities have warned residents, visitors and tourists about the risks of volcanic rocks, heavy ashfall, lava flows and secondary eruptions.
The Geological Agency has prohibited access within a five-kilometre radius of the eruption centre, as well as areas within one kilometre of two newly formed islands to the northwest and southeast of Anak Krakatau.
Coastal communities in Banten and Lampung provinces have also been urged to remain calm, avoid spreading unverified claims about tsunamis and follow official safety instructions.
