The same Anak Krakatau volcano is blamed for an eruption that killed 36,000 people in 1883.
A full moon caused a tidal wave that compounded the problems on Sunday.
Officials say nearly 1,500 people were injured and 57 are missing on the island of Java. The giant wave hit Sunday without warning and damaged more than 600 houses and displaced 12,000 people.
The country’s tsunami warning system has been inoperable because of vandalism and technical problems since 2012, said Sutopo Purwo Nugroho, head of public relations for the Indonesian National Disaster Mitigation Agency.
Indonesian President Joko Widodo ordered the country to purchase new early warning detectors as soon as possible. He said on Twitter that he’s praying for the victims and will be heading to the disaster zone Monday.
President Donald Trump reacted to the disaster on Twitter.
“Unthinkable devastation from the tsunami disaster in Indonesia,” Trump said. “We are praying for recovery and healing. America is with you!”
Pope Francis asked the world to pray for the victims of the disaster.
“My appeal is that these brothers and sisters may not lack our solidarity and the support of the international community,” he said.
Two months ago, a tsunami slammed into the Indonesian island of Sulawesi, killing more than 2,000 people. Indonesia’s worst disaster to date was the 2004 Boxing Day tsunami that killed nearly 230,000.
