Adding to the anguish was a report by a German research center that developed a warning system used by Indonesia that the tsunami alert to some residents of Sulawesi failed after the quake hit on Friday.
Military and commercial aircraft were delivering some aid and supplies.
Nugroho said conditions in the Balaroa and Petobo sections of Palu were particularly bad because the quake caused loose soil to turn into thick, heavy mud that unleashed massive damage.
The tsunami washed this ship onto shore in Wani, Donggala district, on the Indonesian island of Sulawesi. "I want to know if they are safe there".
Indonesian President Joko Widodo authorised the acceptance of worldwide help, Nugroho said, adding that generators, heavy equipment and tents were among the most-needed items.
Three of the victims were recovered alive.
"We have heard nothing from Donggala and this is extremely worrying", said Jan Gelfand, head of the International Federation of Red Cross and Red Crescent Societies Country Cluster Support in a statement.
Neighbors including Australia, Thailand and China offered help and Pope Francis, speaking to thousands in St. Peter's Square, said he was praying for the victims.
In the Petobo neighborhood, Edi Setiawan said he and his neighbors rescued children and adults, including a pregnant woman. "This is for sure a matter of life and death for the prisoners", she said. "My mother was able to survive after struggling against the mud and being rescued by villagers". "Now their cries are no longer heard".
There are fears some survivors may still be trapped under the rubble. The three areas have a combined population of over one million people.The region was struck by at least one moderate aftershock on Tuesday.
Indonesia's disaster agency says the death toll from the massive quake and tsunami has increased slightly to 844, and almost 50,000 people have been displaced by the disaster.
State energy company Pertamina said it was airlifting 4,000 liters of fuel to the area to help with the rescue efforts, while state logistics agency Bulog said it was preparing to send in hundreds of tons of rice.More news: Seattle Seahawks player breaks leg, sends parting message to team
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"Our funding has been going down every year", the disaster agency's Nugroho said.
In Donggala, the site closest to the earthquake's epicenter, aerial footage on Metro TV showed the sugary blond sands of beaches swept out to sea, along with some buildings.
Indonesia, the world's largest archipelagic nation with more than 17,000 islands, lies on the Pacific's "Ring of Fire", where earthquakes and volcanic eruptions are frequent as a result of movements of tectonic plates.
The city is built around a narrow bay that apparently magnified the force of the tsunami as the waves raced into the tight inlet.
Indonesian police unload bodies from a truck to be transfered to a mass grave in Palu in Indonesia's Central Sulawesi on October 2, 2018, after an natural disaster and tsunami hit the area on September 28.
"The ground rose up like a spine and suddenly fell".
Residents in the Indonesian city of Palu have converged on the local airport in a desperate bid to escape with many angry and begging Indonesian President Joko Widodo for help.
The dead - many yet uncounted, their bodies still trapped in the rubble of collapsed buildings - are also a source of concern for authorities.
"In the evening, some of them turned on their cell phones just to give a sign that they were there".
The vast archipelago is home to 260 million people on more than 17,000 islands that stretch a distance similar to that between NY and London.
Access to the affected areas is severely constrained, due to factors including a landslide across the main road into Palu, restrictions on flights into the airport, the destruction of major seaports and lack of communication with these areas.