MILITANTS attacked a health centre used in an ongoing anti-polio campaign in north-west Pakistan today, triggering a gun battle that left a police officer dead. 

Three of the attackers were also killed in the exchange.

No-one immediately claimed responsibility for the attack in Orakzai, a district of Khyber Pakhtunkhwa province and a former stronghold of the Pakistani Taliban.

Local police officer Adnan Khan said the attack had happened in the morning as health workers were gathering before leaving with a police escort for the door-to-door campaign.

No polio worker was harmed, but another police officer was wounded, Mr Khan added.

Militants also stormed a health centre in North Waziristan, another former stronghold of the Pakistani Taliban in Khyber Pakhtunkhwa, snatched guns from officers and warned health workers who had gathered there not to take part in the anti-polio campaign, local police officer Shoib Khan said.

The attackers then left with the weapons they had seized, he said.

Militants in Pakistan often target police and health workers during campaigns against polio, claiming that the vaccination drives are a Western conspiracy to sterilise children.

Pakistan and Afghanistan are the only two countries in the world where the spread of polio has never been stopped.