An Indonesian band called Seventeen was performing on the beach in Tanjung Lesung, a popular resort in Banten province overlooking the Sunda Strait, when a tsunami surged into the back of the stage.
The band was entertaining some 260 staff and family members from a division of the state power company PLN.
"We were singing our second song when suddenly a big wave crashed from behind the stage," Seventeen's lead vocalist Riefian Fajarsyah, also known as Ifan, later told news broadcaster TV One.
A short video widely shared on social media showed the band playing at the moment the wave hit, causing it to instantly collapse.
The water washed inland and dragged along everyone at the location.
The local PLN division holding the party, a transmission unit for western Java, lost 14 people in the disaster.
Eighty-nine people were still missing.
About 157 people, including some badly injured, were already accounted for.
"We continue to keep tabs on staff and search for victims," PLN spokesman I Made Suprateka said.
"We are also restoring the electricity network to make it run as normal," he added.
Seventeen's bassist, M. Awal Purbani, also known as Bani, its road manager and its guitarist were killed in the disaster, the band said in a statement.
The drummer, a crew member, and the vocalist's wife were still apparently missing.
Ifan said he floated on the water for about two hours with dead bodies around him.
When he was finally able to get ashore, he found the bodies of Bani and road manager Oki Wijaya among some debris.
