Pakistan, May 19 -- Gunmen in two separate attacks Monday shot and killed two police officers assigned to protect polio vaccination teams in northwest Pakistan before fleeing, officials said.

The attacks occurred in two areas of Bajaur, a district in Khyber Pakhtunkhwa province bordering Afghanistan, police officer Zafar Khan said, as Pakistan launched a new campaign across the country to vaccinate 19 million children against polio in an effort to eradicate the crippling disease.

The attacks happened when the officers were returning home after protecting polio teams, Khan said.

Health workers and police officers assigned to protect them are frequently targeted by militants who falsely claim the vaccination drives are part of a Western ...