On Tuesday, police fired without warning on supporters of the Pakistan Awami Tehreek (PAT) political party who had attempted to resist police demolition of security barriers erected by PAT in front of its headquarters in the Lahore residential area of Model Town.
The media reported that at least eight PAT members were confirmed killed by gunshot wounds. Another media account reported that 80 PAT members were injured, including 40 with bullet wounds.
Punjab Chief Minister Shahbaz Sharif has ordered a judicial inquiry into the incident.
"The Pakistani authorities need to explain why police officers found it necessary to fire live ammunition directly into a crowd of protesters throwing rocks," said Human Rights Watch. "There are a lot of dead and wounded people in Lahore today, and no clear reason why."
The PAT political party is headed by Tahirul Qadri, an opposition politician and a Muslim cleric. PAT had erected the barricades outside its headquarters more than four years ago.
"Pakistan's security forces have a history of using excessive force against civilians with impunity," the rights body said.
"A transparent and impartial investigation into the Lahore shooting is necessary to prevent even greater distrust of the security forces."