Hundreds of thousands of Nepalese are living without clean water or sanitation as the country struggles to deal with the aftermath of Sunday’s 7.8-magnitude earthquake.
Crucial aid delivery and rescue efforts have been hampered by heavy rain and aftershocks, which have created landslides.
The death toll has passed 5,000, while another 10,000 have been injured.
The United Nations estimates more than 8 million people have been affected.
In Kathmandu, World Vision CEO Tim Costello said officials were struggling to deal with the humanitarian crisis, with bodies being cremated and dumped in rivers.
“When you ask people if the government’s done enough, they basically say the government’s invisible,” Mr Costello said.
“(They said) ‘we paid for our own tarpaulin and food and water and we really need international agencies and the rest of the world to help’.
“Our staff in the regions are getting really desperate, they say ‘nothing is getting out here’ because of landslides and bad weather, it’s been pouring rain.”
Prime Minister Sushil Koirala on Tuesday declared three days of national mourning for victims.
He said the government had been overwhelmed by the disaster, and a lack of expert personnel meant appeals for rescue in many cases couldn’t be met.
Helicopters have been carrying the injured across the mountainous region as well as dropping emergency supplies to isolated communities.
The United Nations said it would provide $15 in emergency funding to enable humanitarian groups to scale up their efforts.
The Australian government has pledged $5 million.
– with AAP