Militants on Monday attacked a team of polio vaccinators in the restive Bajaur tribal region of north-west Pakistan, killing security personnel.
The members of the polio vaccination team were unharmed, officials were quoted as saying by TV news channels.
The attackers gunned down a paramilitary personnel protecting the vaccinators.
Taliban factions in the country’s north-west have banned polio vaccination campaigns over the past two years.
In April, a policeman was killed and another seriously injured when militants attacked a team of polio vaccinators in Mardan town of Khyber-Pakhtunkhwa.
In January, six women and a man working for a NGO involved in the polio vaccination campaign were shot dead in Swabi district.
In December, eight volunteers involved in a polio vaccination drive were gunned down in a string of attacks in the southern port city of Karachi and Khyber-Pakhtunkhwa.
The attacks prompted UN agencies to withdraw their workers from the campaign.