Samsung, LG and four Taiwanese firms have been fined heavily for price-fixing of liquid crystal display (LCD) panels on the Chinese mainland.

These companies have been ordered to pay 144 million yuan in fines and return 172 million yuan of extra payment to Chinese mainland buyers. The government also confiscated 36.75 million yuan of their illegal gains, China's top price regulator said Friday.

The four firms from Taiwan are Chi Mei Optoelectronics, AU Optronics, Chunghwa Picture Tubes and HannStar Display.

The six companies were fined for price-rigging on the Chinese mainland between 2001 and 2006, according to the National Development and Reform Commission (NDRC).