At least three polio workers, including two women, were killed on Tuesday in Pakistan when unknown gunmen opened fire at them in the volatile northwestern Khyber Pakhtunkhwa province.
According to preliminary reports, the team was taking part in an anti-polio campaign when they were targeted in Mansehra's Tal Kot area, Dawn reported.
No one took responsibility for the attack yet but the Pakistani Taliban often attacks health workers and their armed escorts to discourage them from polio vaccinations.
Pakistan is one of only three countries where the crippling disease remains endemic.
Islamist militants consider anti-polio vaccines as a Western conspiracy to sterilise Muslims. Scores of health workers in Pakistan have been killed in the last two years as a result.
Last year, the number of polio cases recorded in Pakistan soared to 306, the highest in 14 years.