KANDAHAR: Two gunmen on a motorbike shot and killed a female polio vaccination campaigner in Afghanistan on Monday and seriously wounded her granddaughter, officials said.

No group claimed responsibility for the attack but militants in some parts of the world believe campaigns against the crippling disease are a plot against Muslims, or an attempt to spy on militants.

The pair, a woman and her teenage granddaughter, were polio eradication-campaign volunteers, going house to house in the southern city of Kandahar when they were shot, said senior provincial health official Abdul Qayum Pukhla.

“Today was the last day of the campaign and as the workers were leaving a house, the gunmen opened fire on them and fled,” Pukhla stated.

Afghanistan and Pakistan are the only two countries in the world that remain polio-endemic, according to the World Health Organisation.

Polio attacks the nervous system and can cause irreversible paralysis within hours of infection. But it can be stopped with comprehensive, population-wide vaccination.

When a global eradication campaign was launched in 1988, the virus paralysed more than 350,000 children in 125 countries annually.

Despite some violent opposition to vaccination in Afghanistan, its anti-polio campaign has had remarkable success for a nation at war.

The number of cases has fallen from 63 in 1999 to just 14 in 2013. Only eight new cases have been confirmed this year, compared to 49 in Pakistan.