Pakistan says more than 19,000 have been killed by Saturday's huge earthquake, and it is feared the death toll could climb much further.
More than 42,000 people are believed to be injured, said the interior minister.
The death toll in Indian-administered Kashmir has risen to more than 550, after the bodies of 250 people were found in one town alone.
Pakistan's President Pervez Musharraf has appealed for greater international help in the relief effort.
Large cargo helicopters, "the bigger... the better", are needed to help reach those in "far-flung and cut-off areas", as well as tents, blankets and medicines for the survivors, he said.
Interior minister Aftab Sherpao told a press conference the death toll in Pakistan and Pakistani-administered Kashmir had now risen to at least 19,136, and 42,397 had been injured.
"It is such a horrendous situation that one cannot imagine. Casualties are increasing by the hour," he said.
'Devoured by earth'
The earthquake's epicentre was close to Muzaffarabad, the capital of Pakistani-administered Kashmir.
The BBC's Nick Bryant, in Muzaffarabad, says many buildings have been reduced to rubble.
The city's cricket stadium is being used to house the homeless and offer relief to the survivors. The injured are waiting to be airlifted to hospitals in Islamabad.
Many of the towns and villages in the surrounding areas bore the brunt of the earthquake and have been virtually razed to the ground.
Only a handful of buildings in the once bustling market town of Balakot are still standing, says our correspondent.
Tariq Farooq, works and communications minister in Pakistan-administered Kashmir, said 30,000 people had died in that region alone.
But there was no confirmation of that figure from the central authorities.
A military spokesman told the BBC that the government's priorities were to evacuate those in need of medical care, establish medical treatment centres on the ground, and provide shelter for thousands of homeless people.
Landslides and rain are hampering relief efforts.
The earthquake, which hit at 0350GMT on Saturday, was felt as far away as the Afghan capital, Kabul, and India's capital, Delhi. Several aftershocks followed.
It is thought to have been the strongest earthquake to hit the region in a century.
At least 400 children died when two schools collapsed in the North-West Frontier Province's Mansehra district. About 200 soldiers are also thought to have been killed by landslides and falling debris.
DEADLY RECENT QUAKES
2004 Asian tsunami, triggered by undersea quake - kills at least 200,000
2003 Bam, Iran - kills 26,271
2001 Gujarat, north-west India - kills more than 20,000
1976 Tangshan, China - kills 242,000
1923 Tokyo - kills 140,000
In Mansehra, shop owner Haji Fazal Ilahi lost his wife, two daughters and his brother when their house collapsed.
"I could see rocks and homes tumbling down the mountains," said Mr Ilahi, who was driving home to his village when the earthquake struck. "When I reached my village, there was nothing left of my home," he told the Associated Press news agency.
In the capital, Islamabad, rescuers worked through the night in the ruins of the upmarket Margala Towers residential complex. Heavy diggers tugged huge chunks of rubble off a mound of collapsed, compacted apartment floors.
A British team of specialists joined Pakistani rescue workers overnight, bringing out alive a man and a woman to cheers and applause on Sunday morning.
More than 20 bodies have been found and about 90 people have been pulled alive from the rubble.
British officials say other voices have been heard from within the rubble, and they are focusing on an area where it is thought two children may still be alive.
The tower blocks were the only buildings to collapse in Islamabad.
Line of Control
In Indian-administered Kashmir, the initial death toll of 300 - among them 15 soldiers - nearly doubled on Sunday, to more than 550.
Some 250 bodies had been discovered in the town of Kupwara, said officials who warned that the death toll could still rise further.
The town of Uri, close to the Line of Control that separates divided Kashmir, was also badly hit, with 104 dead.
The administration is working overtime to restore essential supplies like electricity and water disrupted by the earthquake, says the BBC's Altaf Hussain in Srinagar.
Several countries have sent teams to help in the relief effort.
Both US President Bush and UN chief Kofi Annan expressed their concern over the disaster.
UK: $177,000 and 60-strong team
China: 49 rescuers, dogs, 17 tons of equipment
Japan: 50 rescue workers
Russia: 30 rescuers, sniffer dogs, special equipment
"The people of the United States offer our deepest sympathies for the loss of life and destruction," said George W Bush in a statement.
Mr Annan said he was "deeply saddened by the loss of life" and announced that the UN was sending a team to co-ordinate relief efforts.
President Musharraf said he had personally thanked Manmohan Singh, the prime minister of India - a long-time rival with Pakistan for control over Kashmir - for the offer to help with rescue operations.