(CNN) -- Two men were killed Friday in attacks on polio teams and their police escorts in Pakistan, authorities said.
A policeman was killed and another injured when unidentified gunmen fired on a polio security team in Swabi, in northwest Pakistan's Khyber Pakhtunkhwa province, District Police Officer Sajaad Khan told CNN.
The officers were there to protect polio workers, who have come under increasing attack in the past year.
The second victim, a polio worker, was shot dead by unknown men in Jamrud, in Pakistan's tribal Khyber Agency, a political administration official who asked not to be named told CNN.
Pakistani cricketer-turned-politician Imran Khan, who heads the Tehreek-e-Insaf (PTI) party, condemned the targeting of polio workers in a statement released by his party.
Khan called on Khyber Pakhtunkhwa's chief minister and the federal government to take "strong action" to arrest those responsible and to provide security for polio workers.
The PTI party holds the majority of seats in the coalition running Khyber Pakhtunkhwa's provincial government.
Militants have targeted anti-polio campaigns in Pakistan since U.S. intelligence officials used a fake vaccination program to help in their hunt for Osama bin Laden in 2011. Under cover of the program, the CIA sought to collect DNA samples from relatives of the al Qaeda leader to verify his presence in a compound in Abbottabad.
More than 20 polio workers have been killed since July 2012.
Some mullahs have also preached against the polio campaign, claiming falsely that the oral vaccine leaves Pakistani children sterile.
Last year, a Taliban commander in northwest Pakistan announced a ban on polio vaccines for children in the region as long as the United States continued its campaign of drone strikes.
Pakistan stepped up its eradication efforts after cases spiked in 2011, but cases continue to be diagnosed. At least 16 cases of polio have been reported this year in Khyber Agency.
Polio, which can cause permanent paralysis in hours, remains endemic only in Pakistan, Nigeria and Afghanistan.
CNN's Saima Mohsin and journalist Zahir Shah Sherazi contributed to this report.