Doctors in Afghanistan have told the BBC that many children may have been killed in Wednesday's earthquake.
More than 1,000 people died in the disaster, and heavy rain, threadbare resources and rugged terrain are hampering rescue workers.
Unknown numbers were buried in the rubble of ruined, often mud-built homes by the magnitude 6.1 earthquake.
The Taliban authorities have called for more international aid. Communication networks are also badly hit.
"We can't reach the area - networks are too weak," a Taliban spokesman was quoted by Reuters news agency as saying.
The United Nations is among those scrambling to provide emergency shelter and food aid to remote areas in the worst-hit Paktika province.
Survivors and rescuers have told the BBC of villages completely destroyed near the epicentre of the quake, of ruined roads and mobile phone towers - and of their fears that the death toll will rise further. Some 1,500 people were also injured, officials say.
Most of the casualties found so far have been in the Gayan and Barmal districts of Paktika. Locals report dozens of villages collapsed.
One woman in hospital in Paktika's capital told reporters she had lost 19 family members.
"Seven in one room, five in another, four in another, then three in another, have all been killed in my family," she said from her hospital bed.
"There was a rumbling and my bed began to shake," another survivor, Shabir, told the BBC.
"The ceiling fell down. I was trapped, but I could see the sky. My shoulder was dislocated, my head was hurt but I got out. I am sure that seven or nine people from my family, who were in the same room as me, are dead."
One mother of six who was badly injured in the earthquake, Bibi, told the BBC many in her village had been killed, including seven of her own family members.
"We are very poor. We cannot reconstruct our homes again," she said. "We have nothing to eat."
All her family's food supplies are buried under the rubble.
"There is nowhere to go," she added. "I demand the Taliban rebuild our houses."
The deadliest earthquake to strike the country in two decades is a major challenge for the Taliban, the Islamist movement which regained power last year after the Western-backed government collapsed.
The earthquake struck early on Wednesday about 44km (27 miles) from the city of Khost and tremors were felt as far away as Pakistan and India.
Afghanistan is in the midst of a humanitarian and economic crisis, and Abdul Qahar Balkhi, a senior Taliban official, said the government was "financially unable to assist the people to the extent that is needed".
The head of the UN, António Guterres said the agency had "fully mobilised" over the disaster.
But Mohammad Amin Huzaifa, head of information for Paktika province, told AFP it was proving "very difficult" for rescuers to reach areas "affected by floods because of heavy rains last night".
Afghanistan is prone to quakes, as it is located in a tectonically active region, over a number of fault lines including the Chaman fault, the Hari Rud fault, the Central Badakhshan fault and the Darvaz fault.
Over the past decade more than 7,000 people have been killed in earthquakes in the country, the UN's Office for the Co-ordination of Humanitarian Affairs reports. There are an average of 560 deaths a year from earthquakes.
Even before the Taliban takeover, Afghanistan's emergency services were stretched to deal with natural disasters - with few aircraft and helicopters available to rescuers.
According to the UN, 93% of households in Afghanistan suffer food insecurity. Lucien Christen, from the Red Cross, said Afghanistan's "dire economic situation" meant "they're [Afghan families] not able to put food on the table".