ISLAMABAD - Unknown gunmen in Pakistan killed two police officers guarding polio vaccinators Wednesday during a national immunization campaign in a country where the crippling disease remains endemic.

Local officials say the attack in a remote mountainous district in the northwestern Khyber Pakhtunkhwa province did not harm any health workers. The assailants fled the scene and a police search operation was underway to capture them, added police officer Saeedur Rehman.

There were no claims of responsibility for the deadly shooting.

Highest Polio Cases in the World

Most of the 104 polio cases Pakistan has reported this year were located in the province, which borders Afghanistan.

The total number of cases in 2019 in Pakistan, the highest in the world, represents a dramatic spike compared to only 12 cases in the previous year. In 2014 there were 306 cases.

The Pakistani government launched a five-day immunization campaign on Monday to vaccinate nearly 40 million children under the age of five years against the polio virus across the country of more than 200 million people.

Pakistani Health Minister Zafar Mirza said that more than 260,000 polio workers have been deployed under enhanced police protection to accomplish the task.

“The environmental sampling demonstrate that the intense virus transmission continues all across the country. Polio remains a national emergency for us,” Mirza acknowledged while launching the last immunization campaign of the year.

Deadly attacks on polio teams have hampered eradication efforts in recent years in Pakistan, but officials attribute the latest outbreak of polio cases to the refusal of parents to allow their children to be vaccinated against the disease.

Radical Islamic groups, particularly in rural Pakistan, oppose the anti-polio campaign as a Western conspiracy to sterilize Muslim children.

During the current polio vaccination campaign, Prime Minister Imran Khan’s government has engaged clerics, sports stars and showbiz celebrities broadcasting special messages to counter the disinformation campaign and urge parents to allow their children to be vaccinated.

“We cannot continue to accept this fact that we are among the two last countries in the world which are still struggling to eradicate polio,” Mirza stressed and resolved to make Pakistan polio-free in the coming few years.

Afghanistan is the second polio-endemic country where officials have reported 26 cases so far this year. Polio has also been endemic in Nigeria but no case has been detected in the country since 2016.