More than 270,000 health workers have fanned out across Pakistan in a five-day drive to vaccinate millions of children against polio, officials said on Monday, as the country launches a push to eradicate the crippling disease.

The drive would target 40 million children under the age of five, according to Babar Bin Atta, the prime minister's spokesman for polio matters.

Pakistan and Afghanistan are among only a few countries in the world where polio is still endemic.

The UN-funded vaccination campaign has, however, helped Pakistan to control the spread. The number of newly affected children came down to just eight so far this year compared to 306 in 2014.

Atta said the army, police and paramilitary forces were providing security to health workers as they administered the vaccine.

The disease, which can cripple children for life, is more common in the country's mountainous north-west region near the Afghan border, which until recent years had been under the control of militants linked to al-Qaeda.

The militants have killed a number of health workers and police guarding them because of rumours that the polio vaccine was aimed at making children sterile.

A series of military offensives have been launched against the militants since 2014 to make sure workers could reach children in previously inaccessible areas.

This year four cases were reported in the region, another three in the province of Balochistan and one in the port city of Karachi.

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