New Delhi: A brutal murder of a girl after a gang-rape throws back to the Delhi's Nirbhaya case of December 2012 and even worse than that.

Unidentified men raped and brutalized a 28-year old mentally challenged girl before murdering her at Bahu Akbarpur in Haryana's Rohtak district last Sunday on February 1.

The women's body was found on Wednesday with key organs missing and sticks, stones and condoms were inserted into her private parts.

Police said the Rohtak woman's body was decomposing when autopsy was conducted at Pandit Bhagwat Dayal Sharma Post Graduate Institute of Medical Sciences (PGIMS) in Rohtak on Thursday.

PGIMS's forensic medicines department head Dr S K Dhatterwal said he has supervised or conducted around 30,000 autopsies, but has never seen such brutality in his 29-year career.

According to the doctors, stones were inserted into the slain woman's anus. Her face was eaten by animals and key organs like lungs and heart were found missing. Also, her skull was fractured and there were injury marks on both her thighs and chest.

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It took 5 hours for Doctors to conduct the autopsy."There was a 16cm long and 4cm wide stick-like article in her vagina. We presume that a longer stick was used and it may have broken inside her. We also found a number of condoms in her vagina," said Dhatterwal.

Police offials said that the woman belonged to Nepal's Vardia district and had been under treatment in Haldwani. She had come to Rohtak a few months back to visit her sister, who works as a domestic help in the city.

Rohtak SP Shashank Anand said they have no clue about the identity of the rapists. "We have constituted an SIT to track down the perpetrators," he said. "We have put our best investigators on the job."

Anand said the woman was a victim of aggravated sexual assault. "It is a blind case of rape and murder... We are conducting a scientific probe considering all possible angles."

The cops are investigating the case to know whether one of more people were involved. They have collected CCTV footages from various parts of the city as part of the investigation.

A case under various sections of IPC, including murder, rape and unnatural sexual act and destruction of evidence has been registered against unknown people.

Rs 1 lakh reward has been announced for anybody who provides information about the rapists.