At least 3,326 people are now known to have died in a massive earthquake which hit Nepal on Saturday, say officials.

More than 6,500 people have been injured, according to the National Emergency Operation Centre.

Dozens of people are also reported to have been killed in neighbouring China and India.

Thousands have spent a second night outside after the 7.8-magnitude quake, which also triggered deadly avalanches on Mount Everest.

Vast tent cities have sprung up in Nepal's capital, Kathmandu, for those displaced or afraid to return to their homes as strong aftershocks continue.

"We don't have a choice, our house is shaky. The rain is seeping in but what can we do?" 34-year-old shopkeeper Rabi Shrestha, who was sleeping by the roadside with his family, told AFP news agency.

Rescue missions and aid have started arriving to help cope with the aftermath of the earthquake, the worst to hit Nepal for more than 80 years.

The weather cleared on Monday morning and helicopters are heading out to the Mount Everest base camp to try to bring down 210 stranded climbers.

The roads to the earthquake's epicentre, northwest of the capital, have also been cleared and rescue teams are on their way.

Efforts to dig victims out from under the rubble of collapsed buildings in Kathmandu are also continuing.

But home ministry official Laxmi Prasad Dhakal told Reuters rescuers were "in a really bad shape" after working non-stop for two days. "We are all about to collapse."

Meanwhile, officials have warned that the number of casualties could rise as rescue teams reach remote mountainous areas of western Nepal.

Initial reports suggest that many communities - especially those close to mountainsides - suffered significant quake damage.

"Villages like this are routinely affected by landslides, and it's not uncommon for entire villages of 200, 300, up to 1,000 people to be completely buried by rock falls," World Vision spokesman Matt Darvas said.

A man evacuated by helicopter to Pokhara, 200km from Kathmandu, said almost every home in his village of more than 1,000 houses had been destroyed, Mr Darvas told the BBC.

In Dhading district, 80km west of Kathmandu, people were camped in the open, the hospital was overflowing, the power was off and shops were closed, Reuters news agency reported.

Renewed panic

A powerful aftershock was felt on Sunday in Nepal, India and Bangladesh, and more avalanches were reported near Everest.

The 6.7-magnitude tremor, centred 60km (40 miles) east of Kathmandu, sent people running in panic for open ground in the city.

It brought down some houses that had been damaged in the initial quake.

At hospitals rattled by the aftershocks, staff moved sick and injured patients outside on Sunday afternoon.

Both private and government hospitals have run out of space and are treating patients outside, officials say.

Deepak Panda, a disaster management official, said medical services were "overwhelmed with rescue and assistance requests from all across the country", Reuters reports.

Foreign climbers and their Nepalese guides around Mt Everest were caught by the tremors and a huge avalanche that buried part of the base camp in snow.

At least 18 people were killed and 60 more injured; many people are still missing.

Separately rescue workers have told the BBC that climbers stranded on Everest have been unable to get down because climbing ropes and ladders have been swept away by a series of avalanches.

Tourism Minister Deepak Chanda Amatya told the BBC that more than 50 climbers had been rescued.

Nepal's ruined tourism

At least four out of seven Unesco World Heritage sites in the Kathmandu valley - three of them ancient city squares - were severely damaged.

Nepali Times editor Kunda Dixit told the BBC that the destruction was "culturally speaking an incalculable loss", although he said monuments could be rebuilt.

In Bhaktapur, until now Nepal's best preserved old city, reports say half of all homes have been destroyed and 80% of temples damaged.

Nepal's architectural jewels destroyed

There are 14 international medical teams on the way to Nepal, the UN says, and up to 15 international search-and-rescue have been sent, the UN says.

Offers of help have come in from around the world. Some foreign teams have already arrived and are helping with search and rescue efforts - braving aftershocks at Kathmandu airport that forced some aircraft to circle before landing.

The UN children's agency says nearly one million children in Nepal urgently need humanitarian assistance as they were particularly vulnerable.

The country is running out of water and food, and there are frequent power cuts, the UN says.

Heavy rain earlier on Saturday further worsened conditions with UN officials expressing concern that thunderstorms that could harm people staying outdoors and lead to a shortage of vaccines against disease including diarrhoea and measles.

Offers of aid:

• US: Disaster response team and an initial $1m (£0.7m), according to aid agency USAid
• China: Rescue team reported to have arrived in Nepal
• India: Several aircraft, carrying medical supplies and a mobile hospital, and a 40-strong disaster response team, including rescuers with dogs
• UK: Eight-strong humanitarian team, £5m in aid
• Pakistan: Four C-130 aircraft carrying a 30-bed field hospital, and army doctors and specialists; urban search-and-rescue teams equipped with radars and sniffer dogs; food items, including 2,000 meals, 200 tents and 600 blankets
• Norway: $3.9m (£2.5m) in humanitarian assistance
• Pledges from Germany, Spain, France, Israel and the EU