An angry mob beat two Muslim men to death over allegations of cow theft, officials have revealed – the latest in a series of similar attacks in India.

The killings happened in the northeastern state of Assam, where the men were beaten with sticks and rocks.

A criminal investigation has been launched to find those who carried out the fatal attack on Sunday. One of the men has been named as Abu Hanif.

It happened in the Nagon district, which is 80 miles from the state capital, Gauhati.

Police in the district said that by the time they reached the scene the men were already in critical condition, and were declared dead at a hospital.

This is the third cow-related death in the country in the past month. On April 1, Pehlu Khan, a Muslim cattle trader, was lynched by a mob in the western state of Rajasthan as he transported cattle he had bought at an animal fair back to his home state of Haryana. Khan and his family were small dairy farmers.

The rise in cow-related lynchings and beatings began after the ruling Hindu nationalist Bharatiya Janata Party was voted to power in a landslide victory in 2014. Most of the attacks have been attributed to local Hindu radical groups.

Human Rights Watch said in a report last week that since Prime Minister Narendra Modi’s government took office at least 10 Muslims, including a 12-year-old boy, have been killed in mob attacks in seven separate incidents related to allegations over cows.

Hindus, who form 80 percent of India’s 1.3 billion people, consider cows to be sacred, and for many eating beef is taboo. In many Indian states, the slaughtering of cows and selling of beef is restricted or banned.

Over the last two years vigilante groups, who call themselves cow protectors, have become active in small towns and cities across India. Even lower caste Hindus, who usually carry out undesirable tasks such as skinning dead cattle, have faced mob violence.

Faizul Islam, 40, father of Abu Hanif, who was beaten to death by a mob on Sunday night, sits with his sons outside their home in Naramari village, about 140 kilometers east of Gauhati, in the northeastern Indian state of Assam, Monday, May 1, 2017. Two Muslim men, including Hanif, were beaten to death by a mob in northeastern India over allegations of cow theft, the latest in a series of similar attacks across the country, police officials said Monday. Human Rights Watch said in a report last week that since Prime Minister Narendra Modi's government took office at least 10 Muslims, including a 12-year-old boy, have been killed in mob attacks in seven separate incidents related to allegations over cows. (AP Photo/Anupam Nath)