They said the footage, captured by World Animal Protection (WAP) and Wildlife Conservation Research Unit, University of Oxford (WildCRU), shows that not only is this a major conservation issue but also a devastating animal welfare concern.
The footage was captured by an undercover researcher on a mobile phone.
It shows hunters using axes to cut trees to get to the animal. But failing to do so, they light a fire to smoke it out.
"Suffocated with smoke, beaten and boiled alive - this is a terrifying ordeal... This footage throws spotlight on how truly shocking the practice of hunting pangolins truly is. Not only is this a major conservation issue - it is a devastating animal welfare concern.
"The two species of Pangolins, 'Manis crassicaudata' and 'Manis pentadacytla', found in India have the highest protection with both being listed on Schedule I of the Wildlife (Protection) Act, 1972. We urge the Central and respective state governments to take strict measures to put an end to poaching of pangolins," said Gajender K Sharma, India Country Director at World Animal Protection.
Pangolins are often termed as the world's most trafficked mammal. The clip is part of a two-year study by researchers from WAP and the University of Oxford, into traditional hunting practices in Assam.
Interviews conducted by researchers with over 140 local hunters found that pangolins were largely targeted for their scales that are sold for a premium, with hunters earning the equivalent of four months' salary for a single pangolin.
The animal's scales are made of keratin, the same material that makes human fingernails and hair, and they have no proven medicinal value.
Pangolin meat is also considered to be a delicacy in some countries, and the scales are also used as jewellery and decorations for rituals.
"Increasing demand driven by traditional Asian medicine is making pangolins a lucrative catch. It is easy to see why they are being commercially exploited, as scales from just one pangolin can offer a life-changing sum of money for people in these communities, but it is in no way sustainable.
Reliable estimates of how many pangolins remain in the wild are lacking, although it is thought that over a million individual pangolins were taken from the wild between 2000, and 2013, WAP said.
There are eight species of pangolin, all of which are considered threatened with extinction on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, it said
Animal protection and conservation bodies also called for strong enforcement of national and international laws, removal of pangolins from the pharmacopoeia of the People's Republic of China the traditional medicine handbook for the industry, investment in and promotion of herbal and synthetic alternatives among others.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)