DHAKA - Bangladesh vaccinated some 25 million children on Saturday in the first round of a fresh drive against polio, the incurable disease which re-emerged in the impoverished South Asian nation early last year.

The children will have the second and final vaccination on December 8, health officials said. The children are also being given a Vitamin A capsule to improve their night vision.

Bangladesh, declared polio-free in August 2000, has launched several rounds of vaccinations since the disease re-emerged in March 2006, infecting some 18 children across the country.

Most cases were in eastern areas on the border with India, one of four countries where polio is endemic.

Health officials believe the Bangladesh outbreak may have originated in India, which has reported more than 500 polio cases, a blow to global efforts to eradicate the disease.

Polio affects mainly children under five and causes paralysis in a matter of hours, health officials said.

Helped by the United Nations Children's Fund UNICEF and the World Health Organisation (WHO), Bangladesh engaged some 800,000 health workers and volunteers to complete the latest drive.

"The first round was successful as almost all targeted children were vaccinated at thousands of vaccination centres across the country," a health ministry official said.

Polio spread from India's populous Uttar Pradesh state to neighbouring Nepal and Bangladesh and distant Angola and Namibia in 2006. All were previously polio-free.