China is strengthening oversight of its drug manufacturers. The move comes a day after the U.S. government warns Americans to avoid certain Chinese diet pills that may cause dangerous side effects.

The new regulations are designed to crack down on China's thriving trade in fake and unapproved drugs, which kill thousands of Chinese each year. The drugs are increasingly sold overseas. Chinese state television Wednesday announced that drug manufacturers soon must meet stricter approval standards. Bai Huiliang, an official from China's drug supervision bureau, said Wednesday that the new law will overhaul the pharmaceutical industry and improve the safety of medicines. Mr. Bai said drug manufacturers must undergo sweeping new quality inspections.

Starting September 15, Chinese authorities will increase monitoring of drug production, sales, packaging and advertising. Local governments will be held responsible for ensuring the safety of medicines.

China has a flourishing legal pharmaceuticals industry. However, some rogue manufacturers sell drugs that are illegal counterfeits, or have not been tested properly, or contain banned ingredients.

The new measure comes in the wake of several deaths and hundreds of illnesses in Japan and Singapore, apparently caused by Chinese diet pills.

On Tuesday, the U.S. Food and Drug Administration issued a warning about two Chinese pills believed to contain fenfluramine, a diet medicine banned in the United States in 1997 after it was linked to dangerous heart problems.

China says it uncovered 70,000 cases of fake or unapproved drugs in the first half of this year alone. State media say the government closed 1,300 factories last year for producing counterfeit medicine.

But health experts say many drug manufacturers keep selling their products even after being ordered to shut down. A senior Chinese health official last week said manufacturers often submit legitimate products for inspection, then sell tainted versions once they have received approval. Local government officials often collude with drug manufacturers to share profits, so local officials are reluctant to crack down on illegal practices.