NEW DELHIinfo-icon: An Indian courtinfo-icon has sentenced 11 men to life in prison for killing a Musliminfo-icon meat trader they suspected of transporting beef, in the first convictions over so-called "cow vigilantism".

The men, including a worker from Prime Minister Narendra Modi's ruling party, were found guilty of killing Alimuddin Ansari in the eastern state of Jharkhand in June 2017.

It was one of a series of attacks related to cows, which are considered sacred by Hindus.

The men were charged with murder and rioting, among other offences, under Indiainfo-icon's penal code and a court in Jharkhand's Ramgarh district delivered its verdict on Wednesday.

"The fast-track court handed them the life sentence yesterday," Rajesh Kumar, a senior police officer in Ramgarh told this news agency by phone on Thursday.

"It is the first case in which a court has convicted and punished (perpetrators) for cow vigilantism." The police officer said a dozen men were arrested over the murder but the court deferred its decision on the twelfth accused who is said to be a minor.

India has witnessed a wave of rising tensions over the killing and smuggling of cows in the Hindu-majority country, where their slaughter is a punishable offence in many states, including Jharkhand.

A number of people, particularly Muslims and low-caste Dalits, have been targeted for allegedly killing cows or consuming beef.

Similar cases of cow vigilante violence are at the trial stage, according to Indian mediainfo-icon reports.

Human Rightsinfo-icon Watch urged law enforcers to take prompt action with credible investigations and prosecutions in the pending cases to rein in "those responsible for hate crimes".

"The authorities still have a long way to go before they can convince religious minorities and socially marginalised communities that justice can be assured," it said in a statement late on Wednesday.

Modi's critics say vigilantes have been emboldened by the election in 2014 of his right-wing Hindu nationalist Bharatiya Janata Party, which promised to completely outlaw cow slaughter across India.

The premier has condemned such vigilantism, saying murders in the name of protecting cows were unacceptable, but it has failed to deter some attackers.

In August, villagers in eastern India beat two Muslim cattle truckers to death on the pretext of protecting cows.