The Shanghai Tourism Trade Association and 10 Huangpu River cruise operators have been fined more than 1.74 million yuan (US$269,350) by Shanghai's market watchdog for violating China's anti-monopoly law.

The trade association's water tourism branch was charged with raising and then fixing the prices of Huangpu River tours and forcing its 10 members to implement the single prices, as well as limiting the number of boats that provide extra services like catering and entertainment since 2011, officials from the Shanghai Administration for Market Regulation said.

It's illegal for cruise operators in the city to place fixed minimums on ticket prices. Each tour operator was required to operate only one ship with catering or entertainment services, which is also illegal.

Major cruise operators including Shanghai Huangpu River Cruise and Bashi Shipping were among those implementing single pricing on their tours.

The cruise operators face warnings and suspension of operations by the association for failure to abide by the requirements.

The companies have been ordered to charge at least 128 yuan per passenger, and online tickets must be at least 90 yuan per person.