NEW DELHI - India's Prime Minister Narendra Modi hit out at a spate of attacks by cow-protecting vigilantes on Saturday, urging action against people who used religion as a cover for committing crime.

Critics say killings in the name of protecting cows, considered sacred by India's Hindu majority, have increased since the nationalist premier won power in 2014. Hundreds of people were detained in western India last month when protests against an attack on four low-caste villagers who were taking a cow to be skinned turned violent.

Modi said he would task state governments with investigating anyone linked to the attacks, and urged the public to take action against perpetrators.

He predicted "70-80 percent of them will turn out to be people who are involved in anti-social activities and masquerade as cow protectors to save themselves".  The speech was the first comment on the vigilante attacks from the Hindu nationalist leader, who has been accused of failing to protect religious minorities. Right-wing Hindu groups in India have long demanded a complete ban on the slaughter of all cattle, citing religious scripture.

Cows are considered sacred by Hindus and killing them carries a severe punishment in most Indian states.

But vigilante groups have increasingly been taking the matter into their own hands, and critics say they have been emboldened under Modi's BJP. A police officer was killed in western Gujarat state last month when a protest against an attack on low-caste villagers who were skinning a cow erupted into violent clashes.

At least five Muslim men were killed last year by Hindu mobs on suspicion of eating beef or smuggling cows across the country.

The family of one of them, who was lynched, have been told they could face criminal charges after being accused of slaughtering a cow.

While the majority of India's 1.2 billion population is Hindu, the country is also home to sizeable Muslim, Christian and Buddhist minorities.