A couple who had contracted a free-will marriage was shot dead, allegedly by the woman's family members, in Karachi on Wednesday, in what police suspect is a case of 'honour killing'.

According to police, 32-year-old Amir and his wife, Mukhtiba, 24, were leaving after meeting their relatives in Sukhia Goth off Super Highway when unidentified assailants opened fire on them and fled.

The victims sustained critical bullet wounds and were taken to Abbasi Shaheed Hospital, where they were pronounced dead.

See: Honour killings — The dark side of Hazara

An official of SITE Super Highway Industrial police said the double murder appeared to be linked to the couple's love marriage.

Amir and Mukhtiba had married of their own free will around two years ago, the official said. They had no children and were residing in the Mominabad area of Orangi Town.

The police have registered a murder case against the deceased man's in-laws on the complaint of his father.

One nominated suspect, a brother of the slain woman, has been arrested while her father and uncle are on the run.

Honour killings continue despite new law

Scores of people in Pakistan, an overwhelming majority of whom are women, are still being murdered by relatives for bringing 'shame' on their family, more than a year since new laws came into force aimed at stemming the menace of 'honour killings'.

In October 2016, a joint sitting of both houses of parliament passed two key pro-women bills that had been pending assent for a long time.

The move at that time was cautiously hailed by women's rights activists. More than a year on, however, lawyers and activists say honour killings are still occurring at an alarming pace.

At least 280 such murders were recorded by the independent Human Rights Commission of Pakistan from October 2016 to June 2017 ─ a figure believed to be understated and incomplete.

The legislation mandates life imprisonment for honour killings, but whether a murder can be defined as a crime of honour is left to the judge's discretion.

That means the culprits can simply claim another motive and still be pardoned, according to Dr Farzana Bari, a widely respected activist and head of the Gender Studies Department at Islamabad's Quaid-i-Azam University.