China's top economic planner announced Monday that two domestic medicine firms had been fined for monopoly pricing practices.

Zhejiang Second Pharma and Tianjin Handewei Pharmaceutical were fined a total of 443,900 yuan (65,975 U.S. dollars) for fixing prices for an active pharmaceutical ingredient, said a National Development and Reform Commission (NDRC) statement.

The two companies charged an unfairly high price for Isoniazid, an antibiotic used to treat tuberculosis, and declined sales with no justified cause, the statement said.

The two companies have since restored regular pricing and revived market competition.

Monopoly practices in the pharmaceutical sector have been a focus of China's anti-monopoly supervision for some time. The case will help regulate active pharmaceutical ingredient pricing and ensure a fair environment for medicine purchases and sales, according to the NDRC.

The NDRC has vowed to increase anti-monopoly supervision to protect market order, consumers and businesses.