By Alastair Wanklyn
The tsunami followed the partial collapse of a volcano off the coast. One side of the mountain slid into the sea, pushing a wave towards the shore.
The tsunami destroyed hundreds of homes. Many victims drowned, others were crushed by timber and metal. And when the water receded it pulled an unknown number of people out to sea.
Many survivors are now homeless. A representative on one island nmearby said hundreds of survivors are cut off. They need food and medicine, the official said.
Indonesia's meteorological agency said further tsunamis are possible. Thousands of survivors fled the coast, jamming roads that were already partially blocked with debris.
In the regional capital of Serang, Catholics attended Mass on Christmas Eve and prayed for the victims.
The nation's president, Joko Widodo visited the area. He told disasters agencies to upgrade warning systems.
Indonesia has seismic monitors in areas where tectonic plates meet. But experts say it is difficult to monitor the risk of tsunamis from offshore volcanoes.
This volcano, on the island of Krakatau, has triggered tsunamis many times. When it first erupted in the 1880s waves killed tens of thousands of people.He told disasters agencies to upgrade warning systems.