The spread of multi-drug resistant malaria in south east Asia poses a "major threat" to efforts to eliminate the deadly disease, experts have warned.

Only half of patients in Cambodia, Thailand and Vietnam are being cured by front-line antimalarial drugs because of the “aggressive” spread of resistance in the malaria parasite, Plasmodium falciparum.

The disease is far less common in south east Asia than Africa, where more than 400,00 people died from the disease in 2017 - over 90 per cent of the total deaths worldwide.

But resistance in south east Asia is a concern because it could cross into Africa where it would have devastating effects, according to researchers from the UK and Thailand.

“[The] expansion and further spread of very difficult to treat, highly resistant P falciparum would cause a regional and potentially global health emergency,” the researchers warned in a study in the Lancet Infectious Diseases journal.