A 7.3-magnitude earthquake hit Nepal on Tuesday, killing dozens of people and triggering renewed panic on the devastated streets of Kathmandu.
The temblor came less than three weeks after 8,000 people died when a 7.8-magnitude quake rocked the Himalayan country on April 25.
“It was completely unexpected," 21-year-old nursing student Shristi Mainali told NBC News from Kathmandu. "At first we just felt like a shake, and we thought it was normal, we are having aftershock, but it didn’t stop, so we got up and rushed to our garden. We could see the ground moving, shaking … in that moment you cannot differentiate whether it’s the ground is shaking or it’s your legs shaking."
David Chen, a 32-year-old who is from San Francisco, was at the ancient Changu Narayan outside Kathmandu when the quake hit.
“There had been aftershocks but they had all been very quick, just a few seconds. But this one, it just seemed liked it would never stop,” said Chen, who was in Nepal helping map UNESCO world heritage sites as the director of engineering for San Francisco-based firm Skycatch. “It was really scary.”
Nepal's National Emergency Operation Centre confirmed 37 deaths, with at least 1,117 others injured. It earlier had put the toll at 42. In neighboring India, at least 16 people were confirmed dead after rooftops or walls collapsed onto them. Chinese media reported one death in Tibet.
It struck at a depth of around 11 miles. The April 25 quake was measured at 9.3 miles. Shallower earthquakes tend to cause more damage at the surface.
The USGS initially reported Tuesday's earthquake as being 7.4-magnitude but later downgraded the figure. It was followed over the course of about 30 minutes by further tremors registering magnitudes of 5.6 and 6.3.
Richard Ragan, emergency coordinator for the UN's World Food Programme in Nepal, said that initial reports suggested that some "structures collapsed, probably structures that were already in disrepair." However, he added that Tuesday's quake "doesn’t appear to have cause a lot of damage" in Kathmandu itself.
Search parties fanned out to look for survivors in the wreckage of collapsed buildings in the town of Chautara, which had become a hub for humanitarian aid after last month's quake.
Shockwaves were felt across northern India and as far away as New Delhi — which is located about 550 miles west of the epicenter. Buildings swayed for more than a minute in the Indian capital and people scurried into the streets.
Mark South, a British Red Cross worker based in Kathmandu, said the tremors were big enough to “scare the living daylights out of everybody.”
He said: “From where I’m standing I can’t see any damage but just a lot of very frightened people.”
South added that there had been many smaller aftershocks since the last month's quake but that the latest temblors came after “a few relatively quiet days.”
“People were just starting to relax and get back to some sort of normality,” he said.
Donatella Lorch, a journalist who lives in Kathmandu, told NBC News that she was having lunch on the fifth-floor terrace of a restaurant when the quake hit. After a few moments, she and other diners realized it was much more than an aftershock.
"Then it got worse, and worse, and everyone got up and started screaming and the tables were sliding on the side of the restaurant," she said. "My husband grabbed me and he says, 'We are on the top floor, we are not running down because it could collapse and we would be buried alive.'"
Fellow diners — including some who appeared to be hyperventilating — turned to each other and held hands, Lorch said. "The minute it stopped we all ran down the stairs and there were hundreds of people lining the central main avenue in front of us," she added.
The April 25 quake flattened mountain villages and destroyed buildings, injuring at least 17,860 people. It was Nepal's worst since 1934.
NBC News' Jason Cumming, David Wyllie, Lisa McNally and Amy Perrette, Reuters and The Associated Press contributed to this report.