An Indian woman was gang-raped and then brutally murdered by men who smashed her skull with bricks after she had threatened to inform authorities, police in the northern state of Haryana, said on Monday.

Police have arrested two men for rape and murder in Sonipat town, and six more were being investigated after the victim's mother accused them of involvement, superintendent of police Ashwin Shenvi told Reuters.

The 23-year old woman, a labourer, was taken by the men ─ at least one of whom knew her ─ by car from near her home in Sonipat to the nearby city of Rohtak, where they raped her, Shenvi said.

“When she said to them she would complain, they hammered her skull in with bricks,” he said. “The way that they brutalised her is horrific.” The body was found in an open field on Thursday.

The mother of the victim had previously registered a complaint against one of the accused for pressuring her daughter into marrying him, but the disagreement was settled between the two parties, Shenvi said. Sonipat is 44 kilometres north of New Delhi.

Sexual violence against women is a highly-charged issue in India, where the horrific, fatal gang-rape of a student on a bus in New Delhi in 2012 sparked nationwide protests about entrenched violence against women and the failure of authorities to protect them.

India has enacted tougher jail sentences for rapists and promised to try those accused through “fast-track” courts but rape, acid attacks and domestic violence remain common.

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Indian media also reported a gang-rape in the city of Gurgaon on the outskirts of Delhi over the weekend. On average, 50 crimes against women are registered every day by police in Delhi, including at least four cases of rape, according to a senior official in the federal home ministry.