Towns and villages near the epicentre of Saturday’s earthquake in central Nepal have suffered “almost total devastation”, the Red Cross says.
Assessment teams say they have found survivors in a “desperate situation”.
Nepal says 6,204 people are known to have died in the 7.8-magnitude quake and 13,932 were injured.
But the fate of thousands more in many remote areas remains unknown and the government has warned that the death toll could rise to more than 10,000.
Although rescue teams from Nepal and the international community are operating in the capital Kathmandu and the surrounding area, landslides and poor weather have hampered efforts to reach isolated districts.
The home ministry says that 20 helicopters carrying relief have landed in the districts of Sindhupalchok, Dolakha, Rasuwa, Nuwakot, Dhading and Gorkha.
But correspondents say that there is a severe shortage of helicopters, and although China is expected to send more, Nepal has appealed to other countries for further aircraft.
On Thursday there was good news in the capital when a 15-year-old boy and a woman in her 20s were pulled from the wreckage of two collapsed buildings in Kathmandu.
But there has been growing anger at the government’s response to the disaster, with a number of protests breaking out.
The home ministry said on Friday that rescue and relief operations in Kathmandu would focus on devastated pockets of the city including the areas around the central bus terminal and around historic monuments – where there is a small chance people remain trapped in several collapsed tall buildings.
Searches will also be conducted for survivors around historic monuments in the ancient towns of Patan and Bhaktapur.
In a statement the International Federation of Red Cross and Red Crescent Societies (IFRC) said that Sindhupalchok, north-east of Kathmandu, stood out as one of the worst affected areas.
“One of our teams that returned from Chautara in Sindhupalchok district reported that 90% of the homes are destroyed,” said Jagan Chapagain, head of IFRC’s Asia Pacific division.
“The hospital has collapsed, and people are digging through the rubble with their hands in the hope that they might find family members who are still alive.”
Source: BBC