NEW DELHI — Under mounting criticism for their slow response to a missing persons report filed last week, the police in the Indian state of Haryana arrested eight men on Monday suspected of raping and murdering a mentally impaired woman whose battered body was found in a field.

The victim, a 28-year-old woman from Nepal, was last seen on Feb. 1. Her sister, who cannot be identified under Indian law, informed the police of her disappearance the same day, but said that they took no action until last Wednesday — three days later — when the victim’s remains were found. The woman told reporters on Monday that the police could have saved her sister’s life if they had begun a search immediately.

Dr. S.K. Dhattarwal, head of forensic medicine at the institute where the post-mortem was carried out, said he had not seen such a brutal case in his 29 years of service. “Her body was mutilated,” he said.

Opposition lawmakers have publicized the case as evidence of poor policing in the state, which is led by the Bharatiya Janata Party. Yash Pal Singhal, the director general of police in Haryana, announced the arrests at a brief news conference, but did not reveal details of the arrests or the killing. Among the eight suspects is one Nepali citizen.