A strong aftershock sent boulders tumbling across mountain roads on Wednesday, blocking efforts to rush relief supplies to tens of thousands of homeless Afghans after a devastating earthquake. Officials said the death toll was in the hundreds, not the thousands originally feared.

The 6.1-magnitude quake struck nearly 80 villages Monday in a mountainous region nine miles in radius, leaving 100,000 people homeless or cut off from food supplies. There were 600 confirmed deaths Wednesday, and the United Nations said the toll was expected to reach 800 to 1,200.

By Afghan standards, aid reached the quake-stricken Hindu Kush region with remarkable speed — assisted by U.S. forces in Afghanistan to battle Taliban and Al Qaeda forces and international peacekeepers whose first job is maintaining security in the capital, Kabul.

"We're here, obviously, for a combat mission, but when this unfortunate accident happened, we were standing by with our coalition partners," said Maj. Leanne Smullen, who accompanied two U.S. Chinooks from Bagram air base laden with U.N. medical supplies and tents. The crew also evacuated one injured person.

Despite rough, poorly maintained roads and frequent truck breakdowns, 2,000 tents, 10,000 blankets and 1,000 tons of food reached Nahrin, 105 miles north of Kabul, a little more than a day after Monday's quake, U.N. spokeswoman Stephanie Bunker said. Clothing, mattresses, cooking sets, medical supplies and surgical units also were on the way to Nahrin, some 40 miles from the quake's epicenter.

That's compared with the week it took aid workers to reach villagers after a quake in northern Afghanistan four years ago killed 5,000 people.

Still, the needs were greater than the supplies at hand. U.N. officials said they require 20,000 tents, 160,000 blankets and 10,000 mattresses.

Relief efforts to some regions were being hampered by minefields left over from 20 years of conflict, their threat multiplied by concerns that the mines had been shifted by the quake.

And a new landslide prevented aid workers from reaching Burka, north of Nahrin, where aerial reconnaissance showed half of the homes in eight villages had been destroyed, leaving 800 families homeless. Road crews had just cleared the dirt mountain track to the remote region when a 5.4-magnitude jolt — the strongest of many aftershocks Wednesday — loosened more boulders, said U.N. regional coordinator Fahrana Faruqi.

The United Nations said it remained concerned about conditions in the Panjshir Valley, tucked deep inside the Hindu Kush mountains north of Kabul, where six villages with 3,000 people were destroyed, and Lakankhel, where aid workers estimate up to 70 percent of homes in seven villages were destroyed, affecting 935 families. De-mining teams were already at work in Panjshir, the world body said.

As of Wednesday, 300 people had been treated for injuries at the scene, and 70 of them were treated for more serious injuries, many of them taken out to Pul-e-Kumri, about 25 miles southwest of Nahrin.

While considerable aid had reached Nahrin, residents of the heavily damaged old part of the city complained Wednesday that no aid workers had yet visited or brought tents and food, although the needy are staying just a 20 minute drive from the aid collection point.

They had little patience for Afghan leader Hamid Karzai, who walked through the ruins of their village earlier in the day and declared Thursday a national day of mourning.

"All the people of Afghanistan share your pain," he told a crowd of several hundred survivors and aid workers. But when he said that the people of Nahrin were "very, very brave. They haven't asked for much," he was interrupted by villagers shouting they had no water or electricity, and were in dire need of help.

Throughout the day, residents dug by hand through the rubble, searching for mattresses, carpets and any household goods to establish camps away from the collapsed walls and roofs of their mud-brick houses. But the continued aftershocks made the salvage operations risky.

Clusters of freshly dug graves dotted the slopes around the old town.

Abdel Jalil searched for cookware in the mound of rubble that was his home. All he found were shards. Nearby, the wall of a neighboring house crashed down on his truck, depriving him of his livelihood. He and eight members of his family survived the temblor, but he said they face an uncertain future.

"Our home is this tent here in our yard," Jalil said, indicating a makeshift shelter constructed from blankets. "We don't have any other place to live."