A massive earthquake killed more than 1,341 people Saturday as it tore through large parts of Nepal, toppling office blocks and towers in Kathmandu and triggering a deadly avalanche at Everest base camp.
Officials said the death toll as its currently stands makes Saturday's natural disaster in the quake-prone Himalayan nation's the worst disaster the country has faced in more than 80 years.
But the final toll from the 7.8 magnitude quake could be much higher, and dozens more people were reported killed in neighbouring Indi, China and Bangladesh.
Nepal police spokesman Kamal Singh Bam told AFP that rescue efforts were still underway.
Emergency workers fanned out across the Himalayan nation to rescue those trapped under collapsed homes, buildings and other debris.
Offers of help poured in from governments around the world, with the United States announcing it was sending in a disaster response team.
"Deaths have been reported from all regions except the far west. All our security personnel have been deployed to rescue and assist those in need," Bam told AFP.
Officials said 10 people were killed when an avalanche buried parts of Mount Everest's base camp in Nepal where hundreds of mountaineers have gathered at the start of the annual climbing season.
"We don't have the details yet, but 10 have been reported dead so far, including foreign climbers," Gyanendra Kumar Shrestha, an official in Nepal's tourism department, told AFP.
"We are trying to assess how many are injured. There might be over 1,000 people there right now, including foreign climbers and Nepalese supporting staff."
AFP Nepal bureau chief Ammu Kannampilly, on an assignment to Everest together with a colleague, was among those caught up in the chaos.
"We are both ok... snowing here so no choppers coming," she said in an SMS on approach to base camp. "I hurt my hand - got it bandaged and told to keep it upright to stop the bleeding."
Experienced mountaineers said panic erupted at base camp which had been "severely damaged", while one described the avalanche as "huge".
"Huge disaster. Helped searched and rescued victims through huge debris area. Many dead. Much more badly injured. More to die if not heli asap," tweeted Romanian climber Alex Gavan from base camp.
But the worst damage was in Kathmandu, where the historic nine-storey Dharahara tower, a major tourist attraction, was among buildings brought down.
At least a dozen bodies were taken away from the ruins of the 19th-century tower, according to an AFP photographer who saw similar scenes of multiple casualties throughout the city.
"It was difficult to breath, but I slowly moved the debris. Someone then pulled me out. I don't know where my friends are," Dharmu Subedi, 36, who was standing outside the tower when it collapsed, said from a hospital bed.
At least 42 people were known to have died in India, including 30 in the eastern state of Bihar, while buildings in the capital New Delhi had to be evacuated.
The United States Geological Survey said the shallow quake struck 77 kilometres (48 miles) northwest of Kathmandu at 0611 GMT, with walls crumbling and families racing outside their homes.
The quake tore through the middle of highways in the capital and also caused damage to the country's only international airport which was briefly closed.
Kari Cuelenaere, an official at the Dutch embassy, said the impact had swept the water out of a swimming pool at a Kathmandu hotel where Dutch national day was being celebrated.
"It was horrible, all of a sudden all the water came up out of the pool and drenched everyone, the children started screaming," Cuelenaere told AFP. "Some parts of the city fell down, there was dust rising... There were many (rescue) helicopters."
Aftershock tremors could be felt more than two hours after the initial quake.
USGS initially measured the quake at 7.5 magnitude and later adjusted it to 7.8, with a depth of 15 kilometres.
Nepal and the rest of the Himalayas are particularly prone to earthquakes because of the collision of the Indian and Eurasia plates.
The thrust of the India plate beneath Eurasia generates a large amount of seismic activity, the USGS says on its website.
A spokesman for Nepal's home ministry said the government had released around $500 million as emergency funds for rescue operations.
India dispatched two military transport planes to help with the rescue and relief efforts and there were similar offers from around the region, including Sri Lanka and Pakistan.
The US Agency for International Development (USAID) said a disaster response was being flown to Nepal and that the Obama administration had authorised an initial $1 million "to address immediate needs."
Chinese President Xi Jinping sent a message of condolences to his Nepalese counterpart Ram Baran Yadav and offered to provide assistance.
China's official Xinhua news agency said that 13 people, including an 83-year-old woman, were killed in the Tibet region.
The area has a history of earthquakes, with a 6.8 magnitude quake that hit eastern Nepal in August 1988 killing 721 people. A magnitude 8.1 quake killed 10,700 people in Nepal and eastern India in 1934.