China needs to tackle problems with food and drug quality otherwise it risks serious damage to its credibility on the international stage, the country's top food and drug watchdog has warned.

"Our country is facing a period with high risks for food safety," Sun Xianze, a senior official with the State Food and Drug Administration (SFDA), said.

Sun, director of the department of food safety coordination under the SFDA, made the warning at a seminar on food and drug supervision, held over the weekend.

He said authorities faced an "arduous task" ahead.

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A series of Chinese food exports ranging from pet food to seafood were alleged to contain hazardous chemicals, sparkling wide concerns over the country's food and drug safety.

"The food security problems have impeded Chinese agri-products and food many times in international trade, and damaged our national credibility and image," Sun said.

To ensure better quality of food and drug products, the SFDA has stepped up efforts to push unqualified producers out of the market.

In a statement posted on its website, the SFDA said it had revoked the production licenses of five drug manufacturers since last July and also withdrawn the Good Manufacturing Practice (GMP) certificates from 128 drug makers mainly in Jilin, Henan, Hainan, Sichuan and Anhui provinces.

Eleven people were reported to have died last year after taking a drug made by the Qiqihar No 2 Pharmaceutical Co Ltd, in Northeast China's Heilongjiang Province, one of the five companies shut down by the SFDA.

Guangdong Baiyi Pharmaceutical was reported to have made hemoglobin, which was infected with a virus carried by a donor.

The administration also revoked the production licenses of three factories in Fujian, Henan and Hebei provinces.

The SFDA said it had increased the number of GMP inspectors in pharmaceutical factories and monitored the production quality of narcotic drug makers across the country during the first half of this year.

In another development, the food and drug watchdog has suspended a drug used to treat acute leukemia and rheumatoid arthritis after several adverse reaction cases were found.

Several child patients suffering leukemia in three hospitals in the Guangxi Zhuang Autonomous Region and Shanghai felt pain in their legs and even had difficulty walking after being injected with the methotrexate, a drug produced by Shanghai Hualian Pharmaceutical Co Ltd, according to the SFDA.

The SFDA has ordered the local food and drug administrations in Guangxi and Shanghai to reevaluate the drugs.

Xinhua contributed to the story