Unknown gunmen riding motorcycles Wednesday ambushed and killed seven police officers who were guarding vaccinators during a polio immunization drive in the southern Pakistani port city of Karachi.
Police officials told reporters the fatalities occurred in two separate attacks minutes apart, but no polio workers were hurt.
A breakaway faction of the Pakistani Taliban, Jamaat ul Ahrar, issued a statement claiming responsibility for the violence in Karachi, saying it was part of the group's ongoing attacks on Pakistani police and security forces.
Attacks on anti-polio teams working to immunize children are not uncommon in Pakistan.
In January, at least 14 people, including vaccinators and police officers, were killed and 20 others wounded when a suicide bomber blew himself up near a polio center in the southwestern city of Quetta.
The outlawed Pakistani Taliban claimed responsibility for the attack. The extremist group and others opposing the anti-polio efforts say they suspect the immunization drive is a cover for Western spies, or accuse the government of administering drugs to sterilize Muslim children.
Pakistan and neighboring Afghanistan are the only two countries in the world where polio remains endemic.