The death toll from two major earthquakes in northwestern Afghanistan rose to at least 813 people on Sunday, according to the local authorities, making the dual shocks one of the deadliest natural disasters to hit the country in decades.

The two earthquakes, both 6.3 magnitude, hit Herat Province, along the country’s border with Iran, on Saturday, causing mud-brick homes in several districts to come crashing down and thousands of people in the province’s capital city to rush out of their houses and office buildings as the ground shook beneath them. At least seven tremors followed the initial quakes.

Wakil Safi, 41, who was at home in the provincial capital, Herat City, on Saturday when the earthquakes struck, said he ran outside with his five children when the walls of his home began to tremble, but fell to the ground because of the intensity of the shaking.

“In my 41 years of life, I have never seen such a strong earthquake,” Mr. Safi said. On Saturday night, he and his wife and children — like thousands of others in Herat City — slept outside in frigid temperatures, a blustering wind chilling them to the bone, for fear of additional aftershocks that could bring their homes crashing down. Between the cold and two tremors in the night, they barely slept, Mr. Safi added.

Aid workers who arrived on Sunday in the remote, badly hit areas found scenes of devastation: Homes had been reduced to rubble, and, in some cases, entire families had been killed. Hospitals and clinics — already teetering on the brink of collapse because of shortfalls in funding — were overwhelmed with hundreds of injured people.

In one video circulating on social media, a survivor of the earthquake in a remote village, Wardakha, stood on a pile of rubble that used to be his home. He explained that he was the only surviving member of his family after the quake — all 14 of his relatives, including his 5-day-old child, had been killed when their home collapsed.

The earthquakes were the latest natural disaster to rattle Afghanistan, which has endured enormous floods, mudslides and earthquakes in recent years. In June 2022, a major earthquake struck southeastern Afghanistan and killed more 1,000 people, according to Taliban officials.

The twin shocks follow two other major quakes this year, in Turkey and Morocco, that killed tens of thousands of people combined.

The disasters have compounded the already dire humanitarian and economic crises that have engulfed Afghanistan since the Western-backed government collapsed two years ago, prompting millions of jobs to disappear practically overnight and the prices of basic goods to soar.

Today, nearly half of the country’s 39 million people face severe hunger, including about three million on the brink of starvation, according to the United Nations’ World Food Program.

Since the Taliban seized power in 2021, U.N. officials have said that Afghanistan represents the world’s largest humanitarian crisis. But two years into Taliban rule, aid money has begun to dry up as other crises have seized the world’s attention and the Taliban administration’s mounting restrictions on women have led to calls to cut off funding from the country entirely in response.

As the country heads into the frigid winter months, the suffering is expected to worsen as families are forced to choose between spending the little money they have on food or on firewood to keep their families warm.

The entrenched humanitarian crisis and series of natural disasters have tested the Taliban’s ability to coordinate vast and sustained aid efforts since seizing power in 2021.

After the earthquake on Saturday, Taliban officials said they had directed military and service organizations to prioritize rescue operations, transporting the injured, preparing homeless shelters and delivering food aid in the remote areas that were most affected. On Sunday, officials said that the country’s air force had made 32 flights transporting the wounded and that all relevant agencies were coordinating their response.

But the sudden and dire need for food, aid and shelter appeared to be overwhelming the government’s ability to respond.

“We sent tents, but the number of families was in the thousands, and we could only give tents to some families,” said Musa Ashari, the head of the Taliban’s disaster management department for Herat. “For example, 20 to 30 tents have been given to a hundred families. The rest of them don’t even have a tent to live in.”

At one school turned aid center on the outskirts of Herat City, hundreds of injured people from one of the worst-hit districts, Zinda Jan, lay on dusty blankets waiting for medical help to arrive on Sunday. Many were taken to Baba Ji High School on Saturday by volunteers who had dug them out of the piles of rubble that were once their homes.

Dazed and injured, they were taken to the school — which local leaders had designated as an aid distribution point — because hospitals and clinics were overwhelmed. But nearly 24 hours after they arrived, most had not received any water, medicine or food from government officials, according to a volunteer.

“The conditions are horrible,” said the volunteer, Jami, 44, who preferred to go by her last name for fear of retribution for speaking to the news media.

In many of the hardest-hit areas — mostly villages along mountainous dirt roads and where homes are little more than mud-brick single-story structures — volunteers said little, if any, government aid had arrived.

Qudos Khatibi, 37, a resident of Herat City, traveled to the Zinda Jan District on Sunday morning with other volunteers carrying local donations of water, food and other aid. The devastation, he said, was worse than they could have imagined.

In some villages once home to hundreds of people, there were only a few survivors. The bodies of dozens of children were covered in dust and sheet metal from the religious school they were attending when the quake struck. Village after village was reduced to rubble.

“The situation is very bad,” he said. “You could not tell the difference between a house and an alley.”

Safiullah Padshah contributed reporting.