Three men who were transporting buffaloes in their truck to a slaughterhouse were attacked by vigilantes in the heart of Indian capital New Delhi, the police said on Sunday.

The latest attack comes amidst a wave of rising tensions over cow slaughter in Hindu-majority India, where the animal is considered sacred and its slaughter is a punishable offense in many states.

There have been a spate of attacks in the recent months by ‘cow protection’ vigilante groups, who roam some highways inspecting livestock trucks for any trace of the animal.

A Muslim man died in one such attack earlier this month after the truck carrying cows was attacked by one such vigilante group in western Rajasthan state.

“This incident has nothing to do with any cow protection (group) but is linked to an animal rights’ group which has been working in Delhi for long,” Ramil Baniya, deputy commissioner of police told journalists.

“Around 14 buffaloes were being taken for slaughter when the team of animal rights’ activists intercepted and stopped them, and they had some scuffle and arguments,” Baniya added.

The police have since launched two investigations, one over the alleged illegalities in transportation of buffaloes and the other over attack on cattle truck.

In 2015 a Muslim man was lynched by his neighbors over rumors that he had slaughtered a cow. Police later said the meat was mutton.

Last month a hotel manager was beaten by a mob and his restaurant sealed in Jaipur after Hindu vigilantes accused him of serving beef.

Critics say the vigilantes have been emboldened by the election in 2014 of Prime Minister Narendra Modi’s Hindu nationalist Bharatiya Janata Party.

Last year Modi criticized the cow-protection vigilantes and urged a crackdown against groups using religion as a cover for committing crimes.