Jairam Manjhi, 25, and his 16-year-old girlfriend Parvati Kumari were stopped by Kumari's relatives at a railway station in Gaya district as they tried to run away together on Wednesday morning, police said.

"They were brought back to the girl’s village under heavy protection, beaten to death and then cremated together outside the village," Gaya's Sub-Divisional Police Officer Manoj Kumar Sudhanshu told the Thomson Reuters Foundation.

"This is a clear case of 'honor killing'. They took the law into their own hands."

Manjhi, who was married and had three children, had been in a relationship with Kumari for six months, and this had angered Kumari's family in Amaitha village, police said.

No one in the village tried to stop the attack on the couple, and police heard of it only when someone from a neighboring village reported the crime.

Kumari's aunt has been arrested and police are carrying out raids and searching for 14 other people, some of them Kumari's relatives, police said.

"Honor killings" – when a person is killed by a family member who believes the victim has brought shame on the family, clan or community – are common in parts of South Asia, such as Pakistan, Afghanistan and some regions of India.

Government figures show that 18 "honor killings" were reported in India in 2014. Activists say the crime is under-reported and many such killings are covered up and made to look like suicides from poisoning or hanging.

In India, Khap Panchayats - community groups made up of powerful men who set the rules in villages - are often seen as instigating such killings. Police said preliminary evidence did not suggest the village council was involved in this case.