A group of New York residents is suing Baidu, China’s largest online search engine, for alleged violation of the US constitution, putting a spotlight on China’s wide-ranging and ever stricter internet censorship regime.

In a suit filed in the US district court in Manhattan on Wednesday, the eight plaintiffs accuse Baidu of having violated their right of free speech by excluding their writings and videos about human rights and democracy in China from its search results. The filing lists the Chinese state as co-defendant.

Baidu “proactively censors its content here in the United States in co-operation with and according to [China’s] policies and regulations”, the filing said. It called the company an “agent and enforcer of the anti-democracy policies” of the Chinese government.