The mother of murdered Pune realtor Ketan Agarwal has written to Prime Minister Narendra Modi seeking justice for her son, saying she was "not asking for sympathy or any special favour" but seeking the strictest punishment for those responsible for his killing.

In an emotional letter emailed to the prime minister, Rakhi Agarwal said she never imagined she would have to write seeking justice for her own son.

"Like every mother, I dreamt of watching Ketan build a beautiful life, get married, and grow old with us. Instead, I had to perform the last rites of my child," she wrote.

"My son was brutally murdered, and with him, meri poori duniya chali gayi (my whole world is gone). Every corner of our home reminds me of him... the silence that has replaced his laughter reminds me every day that he will never come back," the distraught mother said.

She also referred to another tragedy in the family, saying her father-in-law died 20 days after Ketan's death as he could not bear the grief of losing his grandson.

"Modi Ji, main sirf ek maa hoon (I am just a mother). I am not asking for sympathy or any special favour. I am only asking for justice," she wrote.

Seeking expeditious justice, Rakhi Agarwal urged the prime minister to ensure the case receives the attention it deserves and that justice is delivered without unnecessary delay.

"Please do not let Ketan become just another case file. He was someone's son, someone's grandson, someone's brother, but to me, woh meri poori duniya tha (he was my entire world)," she said.

The grieving mother said she looks at her son's photograph every night and tells him that his mother is still fighting for him. "One day I hope I would be able to say that you have received the justice," she wrote in the letter.