DHAKA, Bangladesh — Three attackers fatally shot and stabbed the wife of a police superintendent in southern Bangladesh on Sunday morning, the police said, the latest in a series of killings in which Islamist militants are the primary suspects.

The woman, Mahmuda Khanam Mitu, 30, and her young son were walking through a narrow lane near their home in Chittagong on the way to a school bus stop when three men arriving on a motorcycle stabbed her and shot her in the head, said Mohiuddin Mahmood, the officer in charge of the Panchlaish police station in Chittagong. The son was unhurt.