PESHAWAR, Pakistan (AFP) - Gunmen on a motorbike shot dead two health workers during an anti-polio drive in north-west Pakistan on Sunday, the police said, the latest in a series of deadly attacks on vaccination teams.

The killings took place in the town of Gadoon, some 120km east of Peshawar, where door-to-door vaccinations were taking place since Saturday.

"Gunmen on a motorcycle shot dead two health workers who were administering anti-polio drops to children in the area," district police chief Mian Saeed told Agence France-Presse.

The victims, both male, had refused to take security personnel along, he added.

Last month, unknown gunmen killed a female health worker taking part in a World Health Organisation-supported anti-polio drive on the edge of Peshawar, near the restive Khyber tribal region, where the military has been battling homegrown insurgents with links to the Taleban.

No one has claimed responsibility for the latest killings, but last year the Pakistani Taleban banned polio vaccinations in the tribal region of Waziristan, alleging the campaign was a cover for espionage.

Polio teams came under attack in Karachi and in the north-west last year, with the killing of nine health workers carrying out vaccinations.

Pakistan, Afghanistan and Nigeria are the only countries where polio is endemic. Polio cases in Pakistan hit 198 in 2011, the highest figure for more than a decade and the most of any country in the world, according to the United Nations.