The earthquake with epicentre at Lamjung, around 80 kilometers northwest of Kathmandu, had its impact in several cities in Bihar and West Bengal and eastern India. It was also felt in China and as far as Pakistan and Bangladesh.
The quake measured 7.9, the US Geological Survey said. A number of aftershocks were felt for a long time.
Witnesses and media reports said the quake tremors lasted between 30 seconds and two minutes.
Kathmandu's Darbar Square, a UNESCO World Heritage site, was completely damaged in the quake.
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The official said so far more than 150 people have been reported killed.
The earthquake first struck around 11:56 am followed by aftershocks, Nepal Police spokesperson Kamal Singh Ban said.
"There are some casualties in Pokhra. In Gorkha district 10-12 people have been killed," he said. There is a breakdown in communication.
"We are collecting information and mobilising forces for evacuation," he said.
Indian Embassy spokesperson Abhay Kumar said some walls have collapsed in the impact of the major earthquake and the embassy has set up two helplines.
The landmark Dharhara tower in the centre of the capital collapsed and several people are feared trapped.
Nepal's Kantipur TV showed at least 21 bodies lined up on ground after the earthquake.
Doctors at the main civil hospital here said 36 bodies have arrived so far after quake.
Television pictures showed some of the rescued being rushed to hospitals.
Reports said that the quake also caused an avalanche on Mount Everest.