The Kolkata woman did not inform anybody about her brother's death, police said. (Representational)

An elderly woman, believed to be mentally challenged, was found living with the decomposed body of her brother in West Bengal's South 24 Parganas district on Tuesday, police said.

The body was found in an apartment in Narendrapur near Kolkata, after neighbours complained of a stench from the flat. The police believe Anjan Dey, 70, had been dead for two or three days.

"The decomposed body Anjan Dey, 70; a former lawyer was recovered from his flat on the fourth floor of an apartment in Narendrapur. The condition of the body shows that the man might have died at least two to three days back," a police officer said.

Mr Dey's sister allegedly did not inform anybody about the death or perform his last rites.

"The woman is mentally disabled and physically unfit. She has been living with her brother's corpse. Our officers have interrogated her regarding Dey's death but she failed to give a satisfactory answer," the officer said.

Police said there are no external injury marks on the body.

The cause and time of death will be established by the autopsy report.

The incident is a grim reminder of a 2015 case in Kolkata's Robinson Street where a man was found living in his house with the skeletons of his sister and two dogs.