JAKARTA — Indonesia’s Anak Krakatau volcano has shown renewed activity, recording at least 13 eruptions yesterday and prompting authorities to raise its alert status to Level III, the second-highest level in the country’s four-tier volcanic alert system.

The Geological Agency said the alert was raised from Level II effective 9pm local time yesterday, following an assessment of volcanic activity since early this month.

“Signs of increased activity on a low scale began to emerge in early October 2026,” the agency said in its assessment dated October 9.

It noted however, that seismic monitoring had not indicated a significant overall increase in volcanic earthquakes.

Anak Krakatau, located in the Sunda Strait between Java and Sumatra, was downgraded to Level II on September 21 following a reduction in volcanic activity, after remaining at Level III since early September.

The latest activity follows a series of major eruptions in early September that sent volcanic ash into the atmosphere, forcing temporary airport closures. The event disrupted 2,961 flights and affected about 341,000 passengers.

According to eruption reports published on the Volcanology and Geological Hazard Mitigation Centre’s (PVMBG) website, yesterday’s documented eruptions included one at 4.17pm that sent an ash column 250 metres above the summit, followed by another at 4.30pm with a 150-metre column.

Eleven further eruptions were recorded between 6.28pm and 9.20pm, although their ash columns could not be observed. PVMBG’s full-day seismic monitoring recorded 26 eruption earthquakes.

Apart from yesterday’s 13 individually reported eruptions, Anak Krakatau recorded at least five others earlier this month — four on October 5 and one on October 8 — bringing the documented minimum to 18 since the beginning of October.