Hanging Sarabjit Singh would be tantamount to murder of humanity as the Indian national had been convicted without any substantial evidence, Pakistan's leading human rights activist Ansar Burney has said.

Burney, a former minister for human rights, who has been at the forefront of a campaign to commute Sarabjit's death sentence to life imprisonment, has said there were several legal loopholes in his conviction.

Hanging Sarabjit would be tantamount to a murder of humanity as he had been convicted without any substantial evidence, Burney, who was instrumental in the release of Kashmir Singh, another Indian prisoner on death row, told reporters.

"I cannot allow the government to hang Sarabjit Singh on the basis that he is a non-Muslim and non-Pakistani, and because of pressure from extremist fundamentalist groups," he said.

Burney, a member of the Advisory Committee to the United Nations Human Rights Council, condemned protests and threats issued to him by banned terrorist groups and extremist political parties of Pakistan. Pakistani authorities have apparently put off Sarabjit's hanging, which was earlier set for May 1, by up to three weeks.

Sarabjit, 42, was sentenced to death for alleged involvement in four bomb blasts in Punjab province in 1990. His family, which had an emotional reunion with him in a jail in Lahore [Images], has dismissed the charge that he is an Indian spy and insisted that he accidentally strayed across the border in an inebriated condition.