At least eight health workers--including four women--were shot and killed in separate attacks by unidentified gunmen in the northern provinces of Kunduz and Takhar, sources close to the matter said.

The workers were providing polio vaccinations, and the source said the campaign has been stopped in these two provinces.

Local officials in Kunduz confirmed that at least seven workers providing polio vaccinations were killed in three separate attacks by the unidentified gunmen in PD 1 and 2 of Kunduz's capital city, as well as in Imam Sahib district.

“Today at 12:00 noon, in several parts of Kunduz, seven health workers in the polio campaign were killed,” said Qari Obaidullah Abidi, a spokesman for the Kunduz security department.

According to Abidi, two of the health workers--one of them female--were killed in the first incident and two others were killed at a second incident in the capital city-- and three others were killed in the Imam Sahib district of Kunduz.

According to Kunduz's department of security, two perpetrators have been detained as suspects.

Afghans are at risk of contracting polio. Because of decades of war, the remoteness of some living areas, as well as other factors, full-scale vaccination of children has not been completed as elsewhere in the world.