Nigeria has gone three years without a case of polio, putting it on the brink of being declared free of the disease.

This is a dramatic change from 2012 when the country accounted for more than half of all polio cases worldwide, the World Health Organization has said.

The head of the primary health care agency, Dr Faisal Shuaib, said Nigeria had reached a "historic milestone".

But it will be several months before the country can officially be labelled polio-free.

The first criteria, no case for three years, has been achieved.

But now the WHO needs to make sure there is a robust surveillance system in Nigeria to be certain that there are no further cases of the wild polio virus, chairman of Nigeria's polio committee, Dr Tunji Funsho, told BBC Newsday.