Scientists have identified new drug-resistant strains of the parasite that causes malaria.

They found malaria-causing parasites in western Cambodia that are genetically different from other strains around the world.

These parasites could also withstand treatment by artemisinin - a frontline drug in the fight against malaria, the researchers found.

Reports of drug resistance in the area first emerged in 2008. The problem has since spread to other parts of South East Asia.

"All the most effective drugs that we have had in the last few decades have been one by one rendered useless by the remarkable ability of this parasite to mutate and develop resistance," the BBC quoted Dr Olivo Miotto, of the University of Oxford and Mahidol University in Thailand as saying.

As part of the study, published in the journal Nature Genetics, scientists sequenced the genomes of 800 malaria-causing parasites (Plasmodium falciparum) collected from around the world.

"When we compared the DNA of the parasites in Cambodia, they seem to have formed some new populations that we have not really seen elsewhere," Dr Miotto said.

The international team found three distinct groups of drug-resistant parasites present in the area.

The researchers said they did not yet understand what genetic mutations had occurred that enabled the parasites to withstand artemisinin treatment.

But they said that understanding their genetic fingerprint would help them to quickly spot and track these strains if they spread further.