Islamabad: Unidentified gunmen on Saturday shot dead a senior lawyer and his son in the Pakistani port city of Karachi in an apparent sectarian attack, police said.

Salahuddin Haider Jafri, a former president of the local lawyers association, and his son Ali Haider Jafri were heading to office from home when gunmen sprayed bullets at their car in Landhi area.

Witnesses said the father and son were critically injured and died on the way to a nearby hospital.

The gunmen, who were riding a motorcycle, fled after the attack, police officials said.

No group claimed responsibility for the incident.

Police described the incident as an act of terrorism and said sectarian motives could be behind the attack as the slain men belong to the minority Shia community.

A large number of lawyers gathered at the hospital and shouted slogans against the police for their failure to arrest the gunmen.

The lawyers announced they would boycott courts to protest the attack and demanded the arrest of the killers.

Sindh Home Minister Manzoor Wasan condemned the murder and ordered an inquiry.

Karachi, the capital of southern Sindh province and the country's financial hub, has been hit by sectarian and political violence, with extremist and banned groups targeting Shias though there are no tensions between the majority Sunni and Shias.

In a separate incident, gunmen fired at the police guards of a political leader in Landhi area, police officials said.

Two policemen protecting the head of the Muhajir Qaumi Movement-Haqqaqi, Afaq Ahmad Khan, and another man were injured. The injured were taken to a local hospital.

A spokesman for the MQM-Haqqaqi said Khan was heading to Hyderabad, the second largest city in Sindh, when his police escort was attacked.

Khan escaped unhurt in the incident, he said.

Police officer Mirza Majeed said the attack was a terrorist act aimed at creating law and order problems in Karachi.

No group claimed responsibility for this attack and the MQM-Haqqaqi spokesman demanded the government should investigate the incident.

MQM-Haqqaqi is a splinter group of the powerful Muttahida Qaumi Movement and both parties routinely accuse each other of attacks.

The MQM is largely supported by Urdu-speaking migrants from India who settled in Karachi and several other cities after independence from British colonial rule in 1947.