In a shocking discovery made by animal rights groups in the western Indian city of Pune, several stray dogs were tortured and burnt alive, while many others were poisoned to death.

Animal rights activists alerted police after they spotted charred remains and decomposed bodies of at least 21 canines killed in the Baner locality near Pancard Road in Pune.

So far, the authorities found that four dogs were burnt alive and some 16 others were poisoned, but they fear the numbers could rise after dog skeletons were also recovered during the course of investigation, The Times of India newspaper reported.

Members of NGO AaCT India or Action for Animals against Cruelty and Trauma are set to file a formal police complaint on Wednesday (4 October) after they receive postmortem reports of the recovered bodies. The postmortem was conducted on 28 September after the first few bodies were discovered.

"On September 28, we notified the police about the burnt and decomposed dog bodies in the area," AaCT India representative Neena Rai, who visited the spot with other volunteers, told police. "While we were talking to people about the decomposed and charred dog bodies, some workers in the area pointed to an office nearby, saying that people from there had tied the limbs of four dogs, dragged them for 50 metres, poured petrol and set them on fire."

Rai said that when she first visited the spot on 28 September, she saw two stray dogs and another puppy lying dead at different places in a radius of 100 square metres. "On investigating further, we found 11 more dog bodies, which had decomposed 50% to 70%. One dog's head was severed from the torso, its legs tied and broken," she added.

Meher Mathrani, president of AaCT India and animal welfare officer, told the paper that they receive an average of more than 1,000 cases of "extreme brutality towards animals every month".

"These include heinous acts like setting dogs on fire, poisoning them and dragging them live behind vehicles."

The latest incident has shocked animal lovers and volunteers working for animal protection in the city. They have demanded strict punishment for those who carried out the brutal act.