JAKARTA: Indonesian authorities have raised the danger level on a volcano that killed hundreds of people when it triggered a deadly tsunami on Saturday.

Anak Krakatau was spewing ash clouds on Thursday when authorities raised the danger rating to high alert, the second-highest warning level.

Flights around the volcano were rerouted and the previous 2 km exclusion zone was extended to 5 km.

“The volcano shot ash clouds up to 2.5 km high this afternoon. It was higher than usual,” Kristianto, head of western region volcanic mitigation at the Center for Volcanology and Geological Hazard Mitigation, told Arab News.

“We raised the alert status to stop people approaching the volcano,” he said.

The local populace has been told to stay at least 1 km away from the coastline in areas affected by the tsunami, which killed more than 430 people and left more than 20,000 homeless.

Authorities raised the danger level following reports that volcanic ash had fallen on Cilegon and Serang, two industrial towns in Banten province, about 80 km northeast of the crater.

Kristianto said the volcano rumbled back to life in June, but the prevailing winds had carried its plumes of hot ash over the Indian Ocean instead of urban areas in the province.

I Ketut Sukerta, head of the regional disaster mitigation agency in Lampung Selatan, told Arab News that explosions from the eruptions could be heard by communities living in Rajabasa and Kalianda, coastal areas that face the volcanic island.

People who had fled to higher ground on Sebesi, the closest inhabited island to the volcano, had been moved to the mainland in Lampung province, he said.

“We just evacuated 500 people from the island, making a total of about 2,000. We estimate there are still about 1,000 people remaining there,” Sukerta said.

The tsunami on Saturday was triggered when a section of the volcano’s southwestern flank collapsed into the sea, setting off a 4-meter wave that swept up to 500 meters inland on both sides of the Sunda Strait.

Flights over the volcano have been rerouted, but Soekarno-Hatta International Airport in Tangerang, 136 km east of the volcano, and Radin Inten II airport in Bandar Lampung, 100 km north of the volcano, remain open.

Mount Anak Krakatau, or Child of Krakatau, emerged from the sea in 1927 after a massive eruption in 1883 generated a 30-meter tsunami that killed 36,000 people. The volcanic island now stands 380 meters above sea level.