One of Afghanistan's worst earthquakes killed more than 800 people and injured at least 2,800, authorities said on Monday, as rescuers struggled to reach remote areas due to rough mountainous terrain and inclement weather.

The disaster will further stretch the resources of the Afghan interim government, which is already grappling with crises ranging from a sharp drop in foreign aid to deportations of hundreds of thousands of Afghans by neighboring countries.

Sharafat Zaman, spokesperson for the Health Ministry in Kabul, called for international aid to tackle the devastation brought by the magnitude-6 earthquake that struck around midnight local time at a depth of 10 kilometers.

"We need it because here lots of people lost their lives and houses," he said.

The quake killed 812 people in the eastern provinces of Kunar and Nangarhar, administration spokesperson Zabihullah Mujahid said.

Ziaul Haq Mohammadi, a student at Al-Falah University in the eastern city of Jalalabad, was studying in his room at home when the quake struck. He said he tried to stand up but was knocked over by the power of the tremor.

"We spent the whole night in fear and anxiety because at any moment another earthquake could happen," Mohammadi said.

Mudbrick homes collapse

Rescuers were battling to reach remote mountainous areas cut off from mobile networks along the Pakistani border, where mudbrick homes dotting the slopes collapsed in the quake.

"The area of the earthquake was affected by heavy rain in the last 24 to 48 hours as well, so the risk of landslides and rock slides is also quite significant. That is why many of the roads are impassable," Kate Carey, an officer at the UN Office for the Coordination of Humanitarian Affairs (UNOCHA), said. "Rescue teams and authorities are trying to dispose of animal carcasses quickly to minimize the risk of contamination to water resources."

Casualties could rise as rescue teams access more isolated locations, authorities said.

"All our ... teams have been mobilized to accelerate assistance, so that comprehensive and full support can be provided," said Health Ministry spokesperson Abdul Maten Qanee, citing efforts in areas from security to food and health.

Military rescue teams fanned out across the region, the Defense Ministry said, with 40 flights carrying away 420 wounded and dead.

The quake razed three villages in Kunar, with substantial damage in many others, authorities said. At least 610 people were killed in Kunar, with 12 dead in Nangarhar, they added.

Some villagers sat weeping amid the piled ruins of their homes. Others began laboriously clearing the debris by hand, or carried out the injured on makeshift stretchers.

"This is Mazar Dara in Nurgal district. The entire village has been destroyed," one victim told reporters. "Children and elders are trapped under the rubble. We need urgent help.”

Another survivor said: "We need ambulances, we need doctors, we need everything to rescue the injured and recover the dead.”

Appeals for funding

Humanitarian agencies say they are fighting a forgotten crisis in Afghanistan, where the United Nations estimates more than half the population is in urgent need of humanitarian aid.

UN Secretary General Antonio Guterres said the mission in Afghanistan was preparing to help those in areas devastated by the quake.

Afghanistan is prone to deadly earthquakes, particularly in the Hindu Kush mountain range, where the Indian and Eurasian tectonic plates meet.