In Africa, where the majority of global deaths from malaria occur, the disease is mostly spread by a mosquito specific to rural areas.

But the Anopheles stephensi species of mosquito, which is responsible for most of the cases seen in Indian and Iranian cities, breeds in urban water supplies - and is resistant to most insecticides in common use.

The mosquito has already caused cases in Djibouti and Ethiopia to rise, seriously complicating efforts to eradicate the disease.

Researchers say that if it spreads widely in Africa it could put nearly 130 million people at risk.