Michael O'Leary, the World Health Organization Representative in China, has defended the quality of Chinese-made anti-malaria drugs after an international study said substandard and counterfeit products, some originated in China, were undermining intervention efforts in Africa.

Large parts of Africa are threatened by the distribution of fake and poor quality anti-malarials, often made illicitly in China, claimed a study released in January and funded by Wellcome Trust, a global health charity.

Examining such anti-malarials found on sale in 11 African countries between 2002 and 2010, the study found that some contained a mixture of the wrong pharmaceutical ingredients, which would initially alleviate the symptoms of malaria, but would not cure the disease.

But O'Leary said on Monday: "China is a very important manufacturer of quality anti-malarial medicines and plays a substantial role to secure safe and quality drug provision in Africa."

Zhou Xiaonong, director of the parasite-borne disease institute under the Chinese Center for Disease Control and Prevention, said some illegal manufacturers in Southeast Asia might source artemisinin from China, the dominant ingredient being used to make substandard or fake anti-malarias.

Malaria is caused by parasites injected into the bloodstream by mosquitoes and it kills nearly a million people each year, mainly children and pregnant women in African countries.

At present, China has five different anti-malaria drugs pre-qualified by the WHO on the global market, said O'Leary.

The prequalification project, set up in 2001, is a service provided by WHO to facilitate access to medicines that meet unified standards of quality, safety and efficacy for HIV/AIDS, malaria and tuberculosis.

It requires the producing company to make a particular medicine to meet special and very stringent global standards of production, safety testing, quality control and side effects monitoring to ensure drug safety and quality, he explained.

"This is done on a medicine by medicine basis," he added.

"We're happy to see China take the initiative to do so and these pre-qualified medicines made in China are fully strong and effective ones," he stressed.

In return, international institutions like WHO and UNICEF would promote international purchases of medicines which achieve the prequalification level.

But, he also conceded that two other issues have come into play.

First, whether the medicine is used properly, in the correct dosage, which could affect their resistance, and second, substandard or counterfeit medicines intentionally made and sold for profit.

To address both the issues, he called for closer China-Africa cooperation and information sharing to make sure high quality drugs are being taken in proper way.