(CNN)Cow vigilante crimes in India have been ignored or covered up by the authorities, according to a new report.
Between May 2015 and December 2018, 44 people suspected of killing or transporting cows for slaughter, or even just eating beef, were killed in vigilante attacks, according to Human Rights Watch. That number included 36 Muslims.
Human Rights Watch said many of the murders went unpunished in part due to delayed police investigations and "rhetoric" from ruling party politicians which may have incited mob violence.
Many among India's majority Hindu population consider cows to be sacred, and most states have banned their slaughter.
The issue has become a tinder box for the historically fraught relationship between Hindus and Muslims in the country, which has seen numerous instances of communal violence.
Concern has been growing about attacks on Muslims and Dalit minorities, in particular, since Prime Minister Narendra Modi came to power in 2014.
In 2017, 111 people were killed across India and more than 2,300 injured in communal violence of all kinds.
A spokesperson for Modi's Bhartiya Janata Party said "motivated reports" such as the one by Human Rights Watch "always seem to come up when elections are around the corner." India is due to hold a national election before May this year.
The political push by Hindu nationalists to enforce the cow ban is relatively new, with the BJP seizing on it as a way to attract the Hindu vote ahead of the country's forthcoming election, the report said.
"Calls for cow protection may have started out as a way to attract Hindu votes, but it has transformed into a free pass for mobs to violently attack and kill minority group members," said Meenakshi Ganguly, South Asia director at Human Rights Watch. "Indian authorities should stop egging on or justifying these attacks, blaming victims, or protecting the culprits."
Modi's BJP is strongly aligned with conservative Hindu nationalists. More extreme elements in the country believe India should be governed in accordance with strict Hindu beliefs.
In the last national election in 2014, Modi campaigned on a promise to end a "pink revolution" -- a phrase describing the slaughter of cattle across the country.
"When animals are slaughtered, the color of their flesh is pink, and that is why it is called the 'Pink Revolution,'" he said at a rally in the eastern state of Bihar.
Other BJP lawmakers have made more overt threats.
"I had promised that I will break the hands and legs of those who do not consider cows their mother and kill them," said Vikram Saini, a legislator for Uttar Pradesh state, in March 2017.
Brutal violence and police inaction
The Human Rights Watch report focused on 11 attacks in which "police initially stalled investigations, ignored procedures, or even played a complicit role in the killings and cover-up of crimes."
Officers made a priority of filing complaints against the victims and their families for cow slaughter, above arresting the instigators of violence, the report said.
Authorities and alleged vigilantes also intimidated victims so they would not pursue justice, according to Human Rights Watch.
Following one attack in June 2018, in which one person was killed, police allegedly filed a