Hundreds of buildings were destroyed by the wave, which hit the coast of southern Sumatra and the western tip of Java after a volcano known as the “child” of Krakatoa erupted, national disaster agency spokesman Sutopo Purwo Nugroho said.
Search and rescue teams were scouring rubble for survivors, with 222 people confirmed dead, 843 people injured and 28 missing, Nugroho said.
The destructive wave left a trail of uprooted trees and debris strewn across beaches.
A tangled mess of corrugated steel roofing, timber and rubble was dragged inland at Carita beach, a popular spot for day-trippers on the west coast of Java.
Dramatic video posted on social media showed a wall of water suddenly crashing into a concert by pop group “Seventeen” - hurling band members off the stage and then flooding into the audience.
The wave swamped parts of the coast around the Sunda Strait, leaving at least 164 people dead in worst affected Pandeglang district on Java՚s western tip. Large numbers of casualties were recorded at two hotels in the area.
Eleven people died further north in Serang, while 48 were killed in South Lampung, on Sumatra Island.
“This number is predicted to increase because not all victims have been successfully evacuated, not all health centres have reported victims and not all locations have got complete data,” Nugroho said.
Heavy equipment was being transported to badly hit areas to help search for victims and evacuation posts and public kitchens were being set up for evacuees, he added.
Why Does Tsunami Occur? ?
Tsunamis triggered by volcanic eruptions are relatively rare, caused by the sudden displacement of water or “slope failure” , according to the International Tsunami Information Centre.
Unlike those triggered by earthquakes, they give authorities no time to warn residents of the impending threat.
Anak Krakatoa, which forms a small island in the Sunda Strait between Java and Sumatra, emerged around 1928 in the crater left by Krakatoa, which erupted in 1883 killing at least 36,000 people.
“The cause of the undersea landslide was due to volcanic activity of Anak Krakatoa, which coincided with a high tide due to the full moon,” Nugroho told reporters in Yogyakarta.
According to Indonesia՚s geological agency, Anak Krakatoa had been showing signs of heightened activity for days, spewing plumes of ash thousands of metres into the air.
Indonesia is one of the most disaster-prone nations on Earth due to its position straddling the so-called Pacific “Ring of Fire” , where tectonic plates collide.
Most recently in the city of Palu on Sulawesi island a quake and tsunami in September killed thousands of people.
On December 26,2004 a tsunami triggered by a magnitude 9.3 undersea earthquake off the coast of Sumatra in western Indonesia killed 220,000 people in countries around the Indian Ocean, including 168,000 in Indonesia.
How They Deal W⟋this Natural Calamity
Teams of aid workers were helping to evacuate the injured and bring in clean water, tarpaulins and provide shelter, she added, saying the group was preparing for the possibility of diseases breaking out in the tsunami zone.
Mistake of Indonesian Authorities.
Indonesian authorities initially claimed the wave was not a tsunami, but instead a tidal surge and urged the public not to panic.
Nugroho later apologised for the mistake on Twitter, saying because there was no earthquake it had been difficult to ascertain the cause of the incident early on.