Gunmen killed an anti-terrorism court judge and his three family members in northwestern Pakistan on Sunday evening, police said.

Aftab Afridi, the slain judge, and his family were traveling to the capital Islamabad when their vehicle was ambushed by the assailants near Swabi district, located some 51 miles from Peshawar, the capital of northwestern Khyber Pakhtunkwa province, which lies near the border with Afghanistan.

According to the district police chief Muhammad Shoaib, the judge, his wife, son, and daughter were killed in the ambush.

Two bodyguards of the judge were also injured in the ambush.

The attackers managed to flee.

The slain judge was hearing several terrorism related cases as the lead judge of an anti-terrorism court in the scenic Swat valley, once the hotbed of militancy.

The police are investigating the possible motives behind the attack, Shoaib told reporters, adding that the incident seems to be the outcome of an "old enmity".

The judge's family, according to him, have accused their rivals of being involved in the attack.

Meanwhile, Prime Minister Imran Khan condemned the incident on Twitter, assuring the family that the perpetrators of this "gruesome" act will be apprehended and dealt with full "severity of the law."/aa