Wednesday's 5.9-magnitude quake struck hardest in the rugged east along the border with Pakistan, killing more than 1,150 and leaving thousands homeless.
Entire villages have been levelled in some of the worst affected districts, where survivors said they were even struggling to find equipment to bury their dead.
"There are no blankets, tents, there's no shelter. Our entire water distribution system is destroyed. There is literally nothing to eat," 21-year-old Zaitullah Ghurziwal told.
Mohammad Amin Huzaifa, head of information for the province, said heavy rain and floods were hampering efforts to reach those affected.
Communications have also been hit as the quake toppled mobile phone towers and power lines.
The earthquake struck areas already suffering the effects of heavy rain, causing rockfalls and mudslides that wiped out hamlets perched precariously on mountain slopes.
Officials say nearly 10,000 houses were destroyed, an alarming number in an area where the average household size is more than 20 people.
"Seven in one room, five in the other room, four in another, and three in another have been killed in my family," Bibi Hawa told from a hospital bed in the Paktika capital Sharan.
Save the Children said more than 118,000 children were impacted by the disaster.
"Many children are now most likely without clean drinking water, food and a safe place to sleep," the international charity said.
UN "fully mobilised"
The disaster poses a huge logistical challenge for Afghanistan.
The aid-dependent country saw the bulk of its foreign assistance cut off following the Taliban takeover last August, and even before Wednesday's disaster the United Nations warned of a humanitarian crisis that threatened the entire population.
But the quake has prompted an outpouring of sympathy from abroad, although many are wary how any aid will be used.
"The aid distribution will be transparent," government spokesman Bilal Karimi told, adding "many countries have supported us and stood with us".
UN Secretary-General Antonio Guterres said the global agency has "fully mobilised" to help.
According to his office, refugee agency UNHCR has dispatched tents, blankets and plastic sheeting; the World Food Programme has delivered food stocks for about 14,000; and the World Health Organization has provided 10 tonnes of medical supplies sufficient for 5,400 surgeries.
Afghan government officials said Thursday that aid flights had landed from Qatar and Iran, while Pakistan had sent trucks carrying tents, medical supplies and food across the border.