Three religious scholars, including a father and a son, were killed and one injured in a series of violent sectarian attacks in Pakistan's southern port city Karachi on Thursday, according to police.

Four motorcycle gunmen shot the father and son, who were having breakfast at a roadside cafe outside a religious seminary in Karachi's eastern district, the area's police chief Shaukat Ali told Anadolu Agency.

"Maulana Ali Hassan, a veteran religious scholar was the principal of the seminary, while his son Qari Manzoor Ali was a teacher there," the police official said.

Ali said the two died on the spot while one of their employees, who was with them at breakfast, was injured.

“The incident seems to be part of ongoing sectarian killings in the city,” Ali said.

The deceased scholars did not have any active association with political groups but the police said the religious seminary had links with a hardline Sunni group, Ahl-e-Sunnat Wal Jammat, who are anti-Shia.

Hours after the killing of the Sunni scholars, three gunmen fired at a vehicle carrying prominent Shia religious scholar, Taqi Hadi Naqi, in Karachi's central district.

“Naqi received three bullets. He was immediately taken to the nearby hospital but he lost the battle for life,” said the district's police chief Aamir Farooqi.

By Aamir Latif