Parliament attack convict Afzal Guru's hanging "shows a very worrying trend by the Indian government", Human Rights Watch said Saturday.

"The hanging of Afzal Guru, following closely behind the hanging of (Mumbai attack convict) Ajmal Kasab in November, shows a very worrying trend by the Indian government," it said.

"Human Rights Watch opposes the death penalty in all circumstances as an inherently irreversible, inhumane punishment," said Meenakshi Ganguly, the South Asia director of Human Rights Watch.