Brussels, Belgium ? The European Commission fined the Sotheby’s auction house $20.1 million Wednesday for colluding with rival Christie’s to fix commission fees, prices and trading conditions in art sales between 1993 and 2000.

The case follows action in the United States, where Sotheby’s was sentenced to pay $45 million and its chairman was sent to jail and fined.

The collusion between the largest auction houses in the global art market involved agreed increases in commissions paid to sellers of art works as well as trading conditions, guaranteed auction outcomes and conditions of payment, the EU Commission said.

The fine for New York-based Sotheby’s amounts to 6 percent of the company’s worldwide revenue last year, EU spokeswoman Amelia Torres said. Under EU rules, the maximum fine for antitrust violations is 10 percent of a company’s global revenue.

Sotheby’s stressed that it has cooperated with the EU probe.