"To crack down against the pirate DVDs is our job and duty," Lan Yiming, deputy head of Shanghai's culture inspection bureau, said in a telephone interview.

"We want to create a good cultural environment for the international film festival and give guests from home and abroad a good impression," he said.

The eighth edition of the annual Shanghai International Film Festival—the only one of its kind in China's vast entertainment market—runs for nine days starting Saturday. It will feature around 200 selections from South Korea, Germany and Japan.

Hundreds of exhibitors and film industry professionals are due to attend, including Hong Kong action star Jackie Chan, Chinese director Zhang Yimou and Japanese filmmaker Yoji Yamada.

Lan said the anti-piracy sweep also aims to prevent the embarrassment of actors and film professionals attending the festival seeing pirated versions of their films for sale.

As recently as Saturday, the U.S. commerce secretary warned China of a potential political backlash in Washington amid tensions over product piracy and Chinese trade surpluses.

Carlos Gutierrez, in Beijing for official talks, had said U.S. companies are telling him they have not "seen much change" despite Chinese promises to put an end to the illicit trade that they say costs them billions of dollars a year in lost potential sales.

Pirated disks, including high-quality copies of recent Hollywood releases, are usually widely available in Shanghai and other Chinese cities for less than $1.

Many stores also sell authorized copies, although these are usually drawn from a narrow selection of older films that cost several times the price of pirated movies and are usually dubbed into Chinese.