The World Health Organisation (WHO) has formally declared India to be polio-free, with no new cases of the disease detected in the country in the past three years.

The WHO said that the milestone means it now considers the entire south-east Asian region, home to a quarter of the world's population, to be free of the disease.

India's decades-old battle against polio involved a rigorous vaccination campaign carried out by nearly 2.5 million health workers, doctors and volunteers.

It was accompanied by a government-funded advertising blitz that took the message of the importance of polio inoculations to villages and towns across the Indian subcontinent.