"The death penalty is always wrong and the Indian government should immediately stop this execution," a Human Rights Watch South Asia director Meenakshi Ganguly.
"Executing Rajoana would merely continue the cycle of distrust between members of the Sikh community and the Indian state," she added.
Rajoana has been on death row since August 2007 for the assassination of Punjab Chief Minister Beant Singh.
On Tuesday, a Chandigarh court refused a request for a stay of execution and ordered that the hanging proceed Saturday.
On Aug 31, 1995, Beant Singh and others were killed by a suicide bomber in Chandigarh.
Rajoana admitted being part of the conspiracy. He has refused to appeal his conviction and death sentence, saying he does not regret the killing.
The last person executed in India was Dhananjoy Chatterjee, who was convicted in a rape and murder case of a child and hanged in Kolkata in August 2004. The last hanging in Punjab was in 1989.
Human Rights Watch said it opposes the death penalty in all circumstances as an inherently irreversible and inhumane punishment.
"The Indian government has rightly not carried out executions for nearly a decade," Ganguly said.
"It should now officially declare a moratorium, commute all existing death sentences, and then abolish the death penalty for all crimes."
New York: Human Rights Watch Wednesday demanded that India should not hang terrorist Balwant Singh Rajoana.
First Published: Wednesday, March 28, 2012, 14:48