Pakistani authorities should conduct a prompt and impartial investigation into the May 7 killing of human rights activist and lawyer Rashid Rehman, Human Rights Watch said Wedneday.
Those responsible should be fully and promptly prosecuted, it said.
Rehman's killing, an apparent reprisal for his willingness to represent people charged under Pakistan's blasphemy law, underscores the urgent need for the government to repeal that law, Human Rights Watch said.
Two unidentified gunmen killed Rehman in his office in Multan in Punjab province.
Several weeks earlier Rehman had been threatened with "dire consequences" for defending Junaid Hafeez, a lecturer at Bahauddin Zakariya University who was facing prosecution under Pakistan's blasphemy law.
Hafeez allegedly disseminated blasphemous statements via his Facebook account though it is not known what he said, since republishing the statement could lead to blasphemy charges against those who republish it.
"Pakistan's vaguely worded blasphemy law has led to discrimination, persecution, and murder since its imposition almost three decades ago. It should be reformed or repealed immediately," said Brad Adams of Human Rights Watch.
"It is appalling that lawyers who defend the rights of people charged with blasphemy should themselves become the targets of deadly violence."
Rehman's killing follows a spate of recent prosecutions under the blasphemy law, section 295-C of Pakistan's penal code.
"Rashid Rehman's killing underscores that the blasphemy law creates dangers for both defendants and their lawyers," Adams said.
"Killers remain free while those engaged in peaceful expression are targeted by the state and extremists."
