KARACHI, Pakistan (December 18, 2012)--Gunmen killed four women working on a government polio vaccination campaign Tuesday in the Pakistan's largest city, Karachi, Sagher Ahmed, health minister for surrounding Sindh province, said.

Ahmed said the gunmen also wounded two men who were with the women.

The Taliban have spoken out against polio vaccination in recent months, claiming the health workers are acting as spies for the U.S. and the vaccine itself causes harm.

Ahmed says the shootings took place in a Karachi area populated by ethnic Pashtuns.

The Taliban are a Pashtun movement, and many militants are reported to be hiding in these communities in Karachi.

On Monday, police said a gunman killed a volunteer for the World Health Organization's anti-polio campaign in Karachi.