Beijing Tightens Olympics-Ad Grip

See Corrections & Amplifications item below.

HONG KONG -- Beijing has promised to step up efforts to prevent nonsponsors of this summer's Olympics from "ambushing" the more than 60 official sponsors that spent millions for the right to associate their brands with the world's biggest sporting event.

Tuesday, the Beijing Olympics organizing committee, known as Bocog, said it would stop coordinated groups of spectators from wearing uniforms or branded clothing in Games venues this August. That prohibition, announced at a news conference held in conjunction with the China Advertising Association, applies to sponsors and nonsponsors alike.

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"The basic idea is to create a 'clean sports stadium,' which means it is not commercialized," Chen Feng, the deputy chief of Bocog's marketing department, said at the news conference. Audiences won't even be allowed to bring drinks into Games venues, although products from sponsor Coca-Cola Co. will be on sale.

From July 11 through Sept. 17, the authorities will also control billboards in prominent locations to give priority to official sponsors. Athletes and coaches won't be allowed to lend their images to marketing without prior approval from Olympics officials.

Olympics hosts are typically under pressure to protect sponsors, which are a major source of their revenue. While China is often criticized for intellectual-property violations in other areas, the country has taken extra care to protect its Olympics investment. In 2002, China adopted a special law to cover the intellectual property of Olympics symbols.

The Olympics torch relay, which is making its way through China, has witnessed some violations by nonsponsors, including use of the image of the torch in advertising, said Bocog's Mr. Chen. Other examples of ambushing, he said, included companies selling products with the offer of an Olympics ticket.

Sabrina Cheung, director of corporate communications for Beijing Games partner Adidas AG, said the sportswear company "feels confident about Bocog's protection against ambush marketing."

Although Adidas's rivals Nike Inc. and Li Ning Co. have been plastering TV airtime and billboards with promotions featuring Olympic athletes and themes, Ms. Cheung said "there is no question that Adidas is the official sportswear partner for the Beijing 2008 Olympic Games."

To stop subtler forms of ambush marketing, including cases in which smaller companies simply don't understand the rules, Mr. Chen said, "we might also consider using the press to reveal some inappropriate behaviors."

Write to Geoffrey A. Fowler at geoffrey.fowler@wsj.com

Corrections & Amplifications:

China will reserve prominent Beijing billboards for advertisements by Olympics sponsors from July 11 through Sept. 17. An earlier version of this article incorrectly said authorities would control the billboards through Sept. 14.