The devastating 7.9-magnitude earthquake that hit Nepal and surrounding regions on Saturday has killed more than 4,000 people and devastated parts of the country, even as a fresh aftershock hit nearby regions in India.
The US Geological Survey said the earthquake was centred in West Bengal and had a magnitude of 5.1, less severe than Saturday's 7.9 quake in Nepal that has been followed by dozens of aftershocks. The tremors were felt in many parts of West Bengal and Bihar.
Nepal police said 3,904 deaths were counted in the country alone and 7180 people were injured. The quake also destroyed buildings and ancient monuments and ripped apart roads, power lines and other infrastructure.
The aftershocks and rumours about another big quake forced thousands of desperate Nepalese in Kathmandu and other parts of the country to spend the nights in open spaces and under tents as overwhelmed authorities struggled to tackle the devastating situation.
In India, the death toll climbed to 72 with 56 deaths reported in Bihar, 12 in UP, three in West Bengal and one in Rajasthan.
Video: Thousands flee homes, in makeshift tents
Extent of damage
The extent of damage as well as the death toll depend on the state of remote Himalayan villages that rescue workers were still trying to reach. Many of the roads are believed to be cut off by landslides, making it likely that some of these communities can only be reached by helicopter.
The earthquake hit the capital, Kathmandu, but its impact spread far beyond.
At least 18 people died on the slopes of Mount Everest, where avalanches buried part of the base camp packed with foreign climbers. China reported 25 people dead in Tibet.
Nearly 100 aftershocks, including a magnitude-6.7 temblor on Sunday, have hindered rescue efforts and terrorised residents sleeping in open squares and parks.
Kathmandu is full of small, poorly constructed brick apartment buildings, and the quake destroyed swaths of the oldest neighbourhoods, even as more modern structures stood firm. Most areas were without power and water.
Among the capital's landmarks destroyed in the earthquake was the 60-metre (200-foot) Dharahara Tower, built in 1832 for the queen of Nepal.
The quake was the worst to hit Nepal in at least 80 years. Nepal's worst recorded earthquake in 1934 measured 8.0 and all but destroyed the cities of Kathmandu, Bhaktapur and Patan.
Video: Aerial view of devestation in Nepal's earthquake epicentre
1 million children affected
Almost one million children urgently need help after an earthquake claimed more than 3,200 lives in Nepal, the UN children's agency said, as relief workers raced to help the most vulnerable.
With thousands of children camping out in the open in the capital Kathmandu after their homes were destroyed in Saturday's quake, Unicef warned of the risk of disease.
"At least 940,000 children living in areas severely affected by (the) earthquake in Nepal are in urgent need of humanitarian assistance," it said in a statement.
"Limited access to safe water and sanitation will put children at great risk from waterborne diseases, while some children may have become separated from their families."
Unicef said it was mobilising staff and sending two cargo flights with 120 tonnes of humanitarian supplies, including medical and hospital supplies, tents and blankets.
The first aid flights began delivering supplies on Sunday after Kathmandu's airport reopened. Tents and water were being handed out on Monday at 10 locations in Kathmandu, according to district chief administrator Ek Narayan Aryal.
The United Nations said hospitals in the Kathmandu Valley were overcrowded and running out of emergency supplies and space to store corpses.
Most shops in the capital were closed after the government declared a weeklong period of recovery. Only fruit vendors and pharmacies seemed to be doing business.
The first nations to respond were Nepal's neighbours - India, China and Pakistan. The United States, Canada, the United Arab Emirates, Britain, Germany, France, Poland, Italy, Israel and Singapore also sent aid.
India's helping hand
India initiated Operation Maitri, one of the largest relief efforts mounted by the country on foreign soil, with a focus on deploying medical and engineering teams and opening up road links to speed up the evacuation of hundreds of stranded Indian nationals.
A total of 13 heavy lift aircraft, including the C130J Hercules, Il-76 and C-17 Globemaster, several helicopters and hundreds of personnel from the military and National Disaster Response Force (NDRF) are engaged in Operation Maitri.
With hundreds of Indian nationals stranded in Nepal, officials are focusing on opening up damaged roads so that they can be evacuated in buses because the number of flights from Kathmandu airport is limited.
Till Monday morning, the Indian Air Force had airlifted 1,935 people in 12 sorties despite bad weather and an aftershock that briefly shut the Kathmandu airport on Sunday. However, many more Indian tourists and pilgrims are still stranded in the Nepalese capital and other cities.
Plans have been drawn up to evacuate people in 35 buses once roads linking Nepal to the Indian states of Uttar Pradesh and Bihar are repaired and opened.
Defence ministry spokesperson Sitanshu Kar said 6 medical teams, engineering task force components, blankets, tents and other relief materials will be flown to Nepal by the air force on Monday.
India has already provided 10 tonnes of blankets, 50 tonnes of water and 22 tonnes of food donated by states and voluntary agencies.
The Indian Army has already sent 10 Inmarsat systems for satellite communications to Nepal.
Avalanche on Mount Everest
The quake unleashed a devastating avalanche on Mount Everest, killing at least 18 people and injuring dozens. Some warned that dozens of people may still be missing and were almost certainly dead.
The first group of survivors from the avalanche were flown to Kathmandu on Sunday and taken to hospitals. None appeared to have life-threatening injuries.
The avalanche struck near one of the famed mountain's most dangerous spots. It swept down between the Khumbu Icefall and the base camp used by international climbing expeditions.
There were unverified reports of avalanches on other parts of the mountain.
Facebook postings by climbers suggested that some people may have been buried in their tents when the avalanche hit. Climbers and their support teams were leaving the base camp Saturday looking for safer locations.
Reasons behind the temblor
US Geological Survey seismologist Paul Earle said the quake happened on what is known as a "thrust fault." That describes the situation when one piece of the Earth's crust is moving beneath another piece.
In this case, it's the Indian plate that is moving north at 45 millimeters (1.7 inches) a year under the Eurasian plate to the north, Earle said. It's a different type of earthquake than the one that caused the 1906 San Francisco earthquake.
"This is what builds the Himalayan mountain range," Earle said.
The region and particular fault has a history of damaging earthquakes, including four temblors with magnitudes greater than 6.0 in the past 100 years, Earle said, warning that landslides are a particular worry now, given the steep slopes in the region.
Can Nepal recover?
Nepal is a relatively poor country without extensive resources despites its rich cultural heritage and spectacular mountain scenery. It has been plagued by instability in recent years, and general strikes have recently brought chaotic scenes to Kathmandu.
Nepal's constitution was supposed to have been written by the Constituent Assembly that was elected in 2008, following the end of a 10-year Maoist insurgency and the overthrow of the centuries-old monarchy, but the assembly was hampered by infighting and never finished its work.
The current assembly was chosen in 2013, but has faced the same problem.
Rajiv Biswas, Asia Pacific chief economist at business research firm IHS, said long-term reconstruction costs in Nepal using proper building standards for an earthquake zone could be more than $5 billion, or around 20% of the country's GDP.
"With housing construction standards in Nepal being extremely low ... the impact of the earthquake has been devastating based on initial reports," he said in an early analysis of the likely damage.