The official death toll from the twin disasters, which climbed to 1,407 on Wednesday, was expected to rise further as rescue crews continue searching for people trapped beneath the wreckage of collapsed buildings on Sulawesi, a large island east of Borneo. Thousands of people were injured and some 70,000 were displaced from their homes, said Sutopo Purwo Nugroho, a spokesman for Indonesia's National Agency for Disaster Countermeasure.
Rescuers have reached all impacted areas, Sutopo said.
Still, the damage to the region's roads and infrastructure has made it difficult to deliver much-needed humanitarian relief and supplies to survivors in hard-hit areas.
"Moving around the streets the destruction is everywhere," said Zubedy Koteng, child protection adviser for Save the Children Indonesia, who is in Palu, one of the worst-hit cities. "It’s hard to recognize where some buildings once stood, such is the scale of damage. Reaching communities in Sulawesi is really challenging due to its remoteness coupled with the devastation that the tsunami has wrecked, cutting off transport links, which makes children separated from their families even more vulnerable."
Hundreds of children were among the dead and another 46,000 are in urgent need of humanitarian assistance, according to Save the Children Indonesia.
"I’m particularly worried about children who’ve been separated from their families or are now orphans because their parents have lost their lives in this tragedy," Koteng said. "Many of these children are sleeping on the streets because they simply have nowhere to go. It’s hard to imagine a more frightening situation for a child."
On Monday, the bodies of at least 34 children were discovered by Indonesian Red Cross officials inside a church that was buried by a landslide in a remote northern region of Sulawesi.
The children were apparently attending a Christian bible camp when they were killed, Indonesian Red Cross spokeswoman Aulia Arriani told ABC News.
A 7.5 magnitude earthquake struck Central Sulawesi at a relatively shallow depth of 10 kilometers last Friday and triggered a tsunami that slammed into Palu, with waves as high as 20 feet that flooded the coastal city and swept away homes and buildings.
On Wednesday, a volcano erupted on another part of the same island some 585 miles northeast of the quake zone, spitting volcanic ash thousands of feet into the sky.
Earthquakes, tsunamis and volcanic eruptions are common in Indonesia, which is situated on the Pacific Ring of Fire, a seismically-active hot spot encircling the Pacific Ocean. In late 2004, a magnitude 9.1 earthquake off the island of Sumatra triggered a tsunami that killed hundreds of thousands of people in various nations around the Indian Ocean.
ABC News' Julia Macfarlane contributed to this report.