Two women polio workers were killed in northwestern Pakistan when unidentified assailants attacked a vaccination team on Wednesday, according to a media report.
The incident happened in Swabi town of Khyber Pakhtunkhwa province bordering Afghanistan.
Khyber-Pakhtunkhwa Chief Minister Mahmood Khan ordered the authorities concerned to take strict action against the culprits, The Express Tribune reported.
"The polio campaign is in the best interest of Pakistan and we will not let it fail," Khan said.
Pakistan is one of the only two countries where the crippling disease remains endemic.
Attempts to eradicate the disease have been seriously hampered by deadly attacks on vaccination teams in recent years by militants, who oppose the drives, claiming the polio drops cause infertility.
Last year in December, gunmen killed at least two policemen in an attack on a polio vaccination security team in Lower Dir district of the province.