Amid fears of aftershocks, most people remained outdoors as the toll rose to nearly 20,000 on Monday.
The roads leading into Pakistani Kashmir - the area worst affected by Saturday's 7.6 magnitude quake - were blocked by landslides. Power and water supplies have been cut off, and hospitals destroyed.
In many places people dug through the night with their bare hands in an often futile attempt to reach friends and relatives trapped in the rubble, and anger started to build as help failed to arrive.
"Our town has been turned into a heap of rubble and so many people have died but there is absolutely no help in the past two days," said Mohammad Zaheer, a survivor in the shattered town of Balakot.
"We survived the earthquake but now we realise we will die of hunger and cold."
The United Nations said more helicopters were urgently needed to bring rescue equipment and aid to stricken villages high in the Himalayas.
"We are seeing enormous suffering and facing enormous challenges," Jan Egeland, UN coordinator of humanitarian affairs and emergency relief, said. "We're talking about millions affected by this."
He said Pakistan had deployed its own substantial fleet of helicopters to search for survivors, but the scale of the disaster required many more, including small fixed-wing aircraft.
The US responded by offering eight military helicopters - five twin-rotor Chinooks and three Blackhawks based in neighbouring Afghanistan - and two C-130 aircraft loaded with tents, blankets and other relief supplies.
Afghanistan also said it would send four military helicopters, medical teams and three tonnes of medicine.
"We survived the earthquake but now we realise we will die of hunger and cold"
As international rescue teams with sniffer dogs and specialist equipment began arriving in Pakistan, the authorities said more than 19,100 had been confirmed dead and more than 42,000 people were injured.
But Pakistani military spokesman Major-General Shaukat Sultan said the toll would continue to soar, and an official in Pakistani Kashmir said the eventual toll in that region alone would top 30,000.
Kashmir hardest hit
Pakistani officials said more than 11,000 people had been confirmed dead in the town of Muzaffarabad, the capital of Pakistani Kashmir.
"Muzaffarabad is devastated," said the local minister for works and communication, Tariq Farooq.
The earthquake struck on Saturday morning as schools were beginning classes, and hundreds if not thousands of children are feared to have died when buildings collapsed or were engulfed by landslides.
Officials said the hospitals in Muzaffarabad had been hard hit, and the Pakistani military flew in special teams of surgeons and set up field hospitals in the town.
"There's a huge need for field hospitals, water, sanitation and for food," Gerhard Putman-Cramer, head of the UN's Disaster Assessment and Coordination (UNDAC) team, said.
The earthquake also hit Indian-administered Kashmir hard, with officials there saying more than 600 people were confirmed dead.
They also warned many remote villages had yet to be reached and the toll would likely rise.
Offers of aid
The epicentre was close to the Line of Control between India and Pakistan, and scores of soldiers on both sides died when their heavily fortified positions collapsed around them.
Nuclear-armed India and Pakistan have fought two wars over Kashmir, but a peace process is under way and Indian Prime Minister Manmohan Singh has reached out to Pakistan President Pervez Musharraf to offer help.
The UN says millions of people
have been affected by the quake
Offers of aid and assistance have begun pouring in from around the world.
The US said it had provided $50 million in initial aid. The World Bank offered $20 million, while the Asian Development Bank pledged $10 million.
Japan said it had sent a 50-strong emergency relief team and Britain, which has a large South Asian community, said it was sending an initial £100,000 ($176,000) and a 60-strong rescue and relief team.