The rapid spread of "super malaria" in South East Asia is an alarming global threat, scientists are warning.

This dangerous form of the malaria parasite cannot be killed with the main anti-malaria drugs.

It emerged in Cambodia but has since spread through parts of Thailand, Laos and has arrived in southern Vietnam.

The team at the Oxford Tropical Medicine Research Unit in Bangkok said there was a real danger of malaria becoming untreatable

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"It is alarming that this strain is spreading so quickly through the whole region and we fear it can spread further [and eventually] jump to Africa."

About 212 million people are infected with malaria each year. It is caused by a parasite that is spread by blood-sucking mosquitoes and is a major killer of children.

The first choice treatment for malaria is artemisinin in combination with piperaquine.

But as artemisinin has become less effective, the parasite has now evolved to resist piperaquine too.

There have now been "alarming rates of failure", the letter says.

Prof Dondorp said the treatment was failing around a third of the time in Vietnam while in some regions of Cambodia the failure rate was closer to 60%.

Resistance to the drugs would be catastrophic in Africa, where 92% of all malaria cases happen.