India has registered nearly an 800% spike in the number of so-called honour killings reported.
It has led state officials and women's rights groups to call for investigations into how such crimes persist.
Indian police registered 251 cases of honour killings in 2015, compared with just 28 a year earlier when India began counting them separately from murder, according to a statement by junior home minister Hansraj G Ahir to India's parliament.
The surge could partly reflect more willingness by people to report such crimes, which many still consider just punishment for women and men who defy communal customs by marrying outside of their religion, clan or caste.
Often, the perpetrators are relatives seeking to punish young couples for bringing "shame" to the family.
Women's rights activists said the government must pass legislation to recognise the crime as unique in order to target perpetrators for prosecution.
"These figures show that the government has to take this as a priority," said Sudha Sundararaman, head of the All India Democratic Women's Association.
Though police are now asked to count honour killings separately, the lack of a separate law defining such crimes means that some officers still record them in the larger murder category and do not investigate the cases further, she said.
Honour killings are still common enough among Hindus and Muslims to regularly make newspaper headlines in a country where most marriages are arranged by families.
Most cases are reported in northern states such as Uttar Pradesh and Haryana, where caste councils wield enormous power in village life.
The highest number of honour killings recorded last year was in Uttar Pradesh, where police counted 131 killings compared with just two cases in 2014, Mr Ahir said, citing data from the National Crime Records Bureau.
State police officers were sceptical.
Such a jump "is astronomical" and needs to be looked into, Deputy Inspector General DK Chaudhary said.
Women's activists said that is missing the point, and that having 279 honour killings recorded over two years still vastly underestimates the actual numbers.
One 2011 study suggested about 900 people are murdered in honour killings every year in India.
The study by the All India Democratic Women's Association was based on surveys conducted nationwide.
"There is severe under-reporting of such honour crimes. Families are often ashamed to report such crimes," said Annie Raja, of the National Federation of Indian Women.
Ms Raja said the situation had worsened in the last few years, noting an increasing trend in village councils run by unelected elders promoting conservative, anti-women values in the name of preserving Indian culture and tradition.
Some observers also noted that social changes were creating friction in communities, as more women step away from traditional home-making roles to join the workforce.
That makes them more likely to want to delay marriage, while also increasing the chance of finding partners outside of their community.
"There has been a backlash of conservatism," Ms Raja said. "Young people are facing violence and attacks from their families if they fall in love."
Analysts say that even as politicians push for better healthcare and education for girls, they have been unwilling to act against village councils that influence large numbers of voters.
"Indian society is unwilling to accept the choices made by young women when it comes to their marriage," said Ranjana Kumari, of the Centre for Social Research, a New Delhi-based think tank.
"People also have to learn to respect women."