The death toll in Nepal's earthquake could reach 10,000, Prime Minister Sushil Koirala has said, as survivors' despair turned to anger at the government's slow response to the humanitarian crisis unfolding in the country, with food, water and other essentials in desperately short supply.

"The government is doing all it can for rescue and relief on a war footing," Koirala said in an interview with Reuters. "It is a challenge and a very difficult hour for Nepal."