Attempts to get aid to remote areas cut off by the South Asia earthquake are running out of time, the man in charge of the international response has said.
Aid is now arriving for the many thousands affected by the quake
Top UN aid official Jan Egeland warned that "we are losing a race against the clock in the small villages", urging the tripling of aid helicopters.
He was speaking after touring the badly damaged town of Muzaffarabad and nearby villages in Pakistani-run Kashmir.
Survivors are still pouring out of mountain regions, searching for help.
Tens of thousands are thought to have arrived in the wrecked city of Balakot, leaving their dead and some of the injured behind in the mountains where conditions are deteriorating.
"No search team came to our village. Most people have fled and there are only the injured left. Nothing came by helicopter either," said one refugee, Zaman, 28, from Bahngia.
The UN says an estimated two million people need rehousing and a million are in urgent need of help.
Pakistan now says Saturday's earthquake killed at least 25,000 people on its territory while India recorded at least 1,200 deaths.
After seeing the devastation for himself on the ground in Muzaffarabad and flying by helicopter over the scattered villages, Mr Egeland called for urgent help.
He said relief teams were winning in the population centres but warned that hundreds of remote villages have not yet been reached.
"I've never seen such devastation before. We are in the sixth day of operation, and every day the scale of devastation is getting wider," Mr Egeland said.
"We have seen a much graver picture and I believe we need to triple the number of helicopters in the operation. My appeal to the world is to come up with more aid, more relief, and more resources," he said.
Some 20 helicopters have been lent to the aid effort by the international community, but the vast area of destruction is still stretching resources to the limit.
'Forget the divides'
Pakistani troops queued in a field in Muzaffarabad to board a helicopter on Thursday bound for isolated villages in the Neelum valley.
"We are worried for them. We're taking food and supplies with us. We can't reach them by road so we have to use helicopters," an army colonel told AFP.
"The soldiers will be clearing the way for relief workers and channelling through supplies. They will also be clearing the dead bodies," he said, pointing out the face masks many of his men were wearing.
Mr Egeland called for India and Pakistan to put their differences over disputed Kashmir behind them and handle the disaster together.
"We should really forget about old divides in Kashmir and there should be a very open invitation to all assistance from everywhere," he said.
India was among the first countries to offer aid to Pakistan and was sending a second consignment of relief goods on Thursday.
But Pakistan has denied reports from the Indian army that Indian soldiers had crossed Kashmir's Line of Control (LoC) to offer help to their adversaries, helping them build shelters against the cold.