Nearly nine out of 10 European companies operating in China say the country’s Internet restrictions are hurting business, a new survey has found, providing another indication that Beijing’s intensified efforts to exert control online are having an impact beyond freedom of speech.

Conducted by the European Chamber of Commerce between Jan. 28 and Feb. 6, the survey found 86% of companies had experienced negative business effects as a result of blocked websites or online tools, up 15% compared to June. The survey didn’t specify...