ISLAMABAD: A joint session of parliament unanimously passed legislation against 'honour' killings three months after the high-profile murder of an outspoken social media star.

The joint session, broadcast live on television, approved the new anti-honour killing law, removing a loophole in existing law that allows family members to pardon a killer.

"Laws are supposed to guide better behaviour, not allow destructive behaviour to continue with impunity," former senator Sughra Imam, who initially tabled the bill, told media.

Some 500 women are killed each year in Pakistan at the hands of family members over perceived damage to 'honour' that can involve eloping, fraternising with men or any other infraction against conservative values that govern women's modesty.

In a majority of cases, the victim is a woman and the killer is a relative who escape punishment by seeking forgiveness for the crime from family members.