JAKARTA — The sea rose up without warning Saturday night, crashing into coastal villages on Indonesia’s two most populous islands. It killed at least 220 people, washing away buildings, roads and a rock concert on the beach, officials said Sunday evening. The tsunami that struck the western tip of Java and the southern tip of Sumatra was believed to have been triggered by an underwater landslide from the flank of an erupting volcano. Officials in Jakarta said hundreds more people were injured and 30 were missing after the tsunami, the latest in a string of deadly disasters that have killed thousands in Indonesia this year. About 600 buildings were damaged, officials said. Soldiers and rescue workers moved quickly to clear roads blocked by debris; television and social media video showed survivors pulling at wreckage trying to find loved ones. “People are still afraid to go back to their homes since there were still rumors that a tsunami might strike again,” said Aulia Arriani, a spokeswoman for the Indonesian Red Cross.