Pakistani officials say unidentified gunmen have opened fire on polio vaccination workers, killing at least five people.
Police say at least three people were killed in a series of attacks in the port city of Karachi Tuesday and a fourth person died in a similar incident in the northwestern city of Peshawar. Several health workers were wounded.
Authorities say a fifth polio worker was shot and killed in Karachi Monday. Investigators say most of the attacks appear to have been carried out by gunmen on motorbikes.
There was no immediate claim of responsibility, but the attacks have taken place during a three-day nationwide anti-polio drive.
The Taliban has condemned previous polio campaigns as cover for spying.
The militant group began voicing opposition to the health program after a Pakistani doctor was imprisoned for helping U.S. intelligence agents run a fake hepatitis vaccination program aimed at locating then-fugitive al-Qaida chief Osama bin Laden. Some militants also blame the vaccine itself for causing harm.
In July, armed men killed a Pakistani doctor working for the World Health Organization on a national immunization campaign.
The health minister of Sindhi province stopped the anti-polio drive in the Karachi region, on Tuesday, as a result of the shootings.
Meanwhile, officials say the death toll from a marketplace explosion in northwest Pakistan on Monday has risen to 21.
The car bombing attack occurred near government offices in the town of Jamrud, part of the Khyber tribal district. More than 40 people were wounded.
No group has claimed responsibility for the attack.
Khyber is home to various Islamic militant groups, including the Pakistani Taliban, which have waged a bloody insurgency against the government for several years.