Islamabad, Sep 11 (IANS): A polio worker and a policeman were killed in firing by unknown gunmen in Pakistan's northwest Khyber Pakhtunkhwa (KP) province, according to police officials on Wednesday.

Unknown miscreants riding on a motorcycle opened fire at a polio vaccination team in Salarzai area of Bajaur district of the province, said the police in the area.

The attackers fled the scene after carrying out the attack, and a search operation is underway to arrest the culprits, said the police, adding that polio vaccination has been halted in the area after the incident.

Earlier on Monday, a week-long polio vaccination campaign was launched in the district to administer vaccination drops to children aged up to five years, Xinhua news agency reported.

This is the second attack on an anti-polio team in KP province this week. Earlier on Tuesday, a bomb blast hit a vehicle carrying polio workers and policemen in South Waziristan district, leaving at least six people injured, according to police officials.

According to government officials, Pakistan is one of the only two polio-endemic countries in the world along with its neighbor Afghanistan. The country has reported 17 polio cases so far this year.