The earthquake struck roughly half-way between Pokhara and the capital Kathmandu. Communication lines were damaged by the powerful tremor, initially put at magnitude 7.5 by the United States Geological Survey. The USGS later revised this figure up to 7.9, with such readjustments common in the moments after earthquakes.

Early witness reports suggested that many buildings sustained damage in Kathmandu. People as far away as New Delhi and the northern Indian city of Kolkatta reported having felt tremors afterwards.

Journalist Guna Raj Luitel shared an image on Twitter after the quake from Kathmandu, saying he was just able to get to safety.

Nepalese Information Minister Minendra Rijal told India's NDTV station that there were reports of damage but that it was too early to estimate on casualties; he said rescue teams were on the scene. NDTV also reported that the city's Tribhuvan International Airport was closed to traffic because of damages.

The Dharahara, or Bhimsen Tower - a renowned 19th-century nine-story building in Kathmandu - was severely damaged on Saturday. Nepalese media reported that at least 50 people were trapped inside. Built as a watch tower in 1832, it was commissioned by the prime minister of the time, Bhimsen Thapa, on the orders of Queen Lalit Tripura Sundari.

The tremor hit at 11:55 a.m. local time (0611 GMT/UTC). The USGS estimated its depth at 15 kilometers (9.3 miles). Its epicenter was roughly 80 kilometers (50 miles) west-north-west of Kathmandu. Information Minister Rijal told the BBC that he feared damage was likely worse closer to the quake's source.

The USGS registered seven more aftershocks, the largest of magnitude 6.6, within two hours of the initial quake. National radio in Nepal warned people to stay outdoors and maintain calm because more aftershocks were feared.

Nepal's Kathmandu Valley lies on a major fault line. A 1934 quake - of magnitude 8.4 - destroyed more than 80,000 buildings and claimed around 8,500 lives, according to the UN. Nowadays, Kathmandu is a far more densely populated region, home to around 2.5 million people. Many buildings in the region are of poor quality.

Nepalese annual GDP per capita in 2013 was put at $694 (638 euros) by the World Bank - or less than $2 a day.

msh/gsw (AFP, AP, Reuters)