Gunmen on motorcycles have gunned down seven police officers guarding a children's polio vaccination team in Pakistan's southern city of Karachi.
Police said the gunmen carried out the killings in two separate attacks minutes apart on April 20 in the city's western Orangi Town neighborhood.
The attackers opened fire on a police vehicle, killing all four officers inside, and three other policemen who were on duty in the area.
No polio workers were harmed.
No one so far claimed responsibility, but militants in Pakistan have regularly targeted polio workers and their guards.
Militants say the polio vaccination campaign is a cover for Western spies or a conspiracy to sterilize Pakistani children.
Pakistan and Afghanistan are the only two countries where the disease is still endemic.