WASHINGTON - Baidu Inc, China's biggest search engine, and Alibaba Group Holding Ltd's Taobao, the nation's largest e-retailer, have been named "notorious markets" by the US Trade Representative (USTR) for helping sustain piracy and counterfeiting.

The Chinese companies were among more than 30 Internet and physical markets worldwide identified by the USTR for helping the illegal sale of goods or materials protected by copyright or patents. Others on the list include the Pirate Bay file-sharing website in Sweden and the Silk Market in Beijing, according to the statement.

The US agency called on the regulators overseeing the markets included in its list to pursue possible legal action and step up efforts to combat violations. The spread of global piracy and counterfeiting hurts entrepreneurs and industries worldwide, said Ron Kirk, the US trade representative.

"There's always some concern on investors' minds about fraud," said Aaron Kessler, an analyst at ThinkEquity LLC in San Francisco. "That's existed in China to a larger degree than with US companies."

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Zhao Xianquan, a spokesman at China's Ministry of Commerce, wasn't available for comment on the topic.

Baidu, China's most visited website, provides "deep linking" to items on sites that are being sold without the permission of the copyright holders, according to the statement. Taobao has a "long way to go" to stamp out the availability of infringing goods on its website, though the company is making "significant efforts" to resolve the problem, according to the statement.

"We will continue to work closely with brand owners and others to further raise the level of trust and integrity in our online marketplaces," John Spelich, a Hong Kong-based spokesman for Alibaba, said on Tuesday.

Other websites listed include torrentz.com; ThePirateBay, which has been the target of a "notable criminal prosecution" in Sweden; 91.com; and the Russian-based Rutracker, according to the statement.

Bloomberg News