At least 700,000 health workers fanned out across Bangladesh on Saturday to immunise 24 million children against polio in a bid to tackle a surprise resurgence by the disease, an official said.
Eighteen new cases reported since January last year, the first since 2000, have prompted the latest campaign by health authorities here.
"Across Bangladesh, we have set up over 140,000 health centres where parents are bringing their children for administering polio vaccines," the government's immunisation programme manager Abdul Qader said.
Hundreds of thousands of schools, mosques and temples joined Bangladesh's non-government organisations to help.
Volunteers will visit door-to-door in the next four days to find out if any child has been left unprotected.
The government has laid special emphasis on immunising children along its 4,000-kilometre (2,500-mile) border with India, which also has launched an immunisation drive following a surge in polio cases.