The Chinese government called on the United States on Monday to explain its actions and halt the practice of cyberespionage, after news reports said that the National Security Agency had hacked its way into the computer systems of China’s largest telecommunications company. The reports, based on documents provided by the former security contractor Edward J. Snowden, related how the spy agency penetrated servers owned by the company, Huawei, and monitored communications by its senior executives in an effort to discover whether the executives had links to the Chinese military. The operation also sought to exploit the company’s technology and gain access to the communications of customers who use Huawei cellphones, fiber optic cables and network hubs. American officials have been working to block Huawei from entering the American telecommunications market.