Agartala: A 70-year-old man of Tripura's Sepahijala district was detained on Friday after his granddaughter was found hanging from the ceiling in their house, police said.

A BJP Yuva Morcha leader and the neighbours alleged that the man sexually assaulted the 16-year-old girl, strangled her to death, and hanged her body to make it look like suicide.

They demanded capital punishment for the grandfather.

No formal complaint was lodged by the victim's family, and the police registered an unnatural death case. "After being alerted, a police team reached their house on Thursday night and recovered the body. Preliminary findings indicate it was a hanging case. The actual cause of death will be confirmed after receiving the post-mortem examination report," Officer in Charge (OC) of Sonamura Police Station, Tapas Das, said over the telephone.

"The victim's 70-year-old grandfather has been detained for interrogation," he said.

The class 10 student used to live in the house with her grandfather and grandmother. Her parents live elsewhere.

Sukanta Sarkar, the president of the BJP Yuva Morcha unit of Nalchar Assembly constituency, alleged that the girl was first raped and then murdered by her grandfather.