(CNN) -- Militants gunned down a polio worker Saturday in the tribal area of Pakistan, officials said.
The attack occurred in a village in Jamrud Tehsil area of Khyber Agency.
The polio worker was seriously injured, and succumbed to his wounds at a local hospital.
Local political official Jehangir Azam Wazir confirmed that the polio worker died of bullet wounds.
Intelligence sources said the attackers left a pamphlet warning that those taking part in polio vaccinations or working for any nongovernmental organizations will be targeted.
Earlier, militants kidnapped teachers who supported a polio drive, but released them following intervention by local elders.