HONG KONG — The Chinese government has adopted new regulations requiring companies that sell computer equipment to Chinese banks to turn over secret source code, submit to invasive audits and build so-called back doors into hardware and software, according to a copy of the rules obtained by foreign technology companies that do billions of dollars’ worth of business in China.

The new rules, laid out in a 22-page document approved at the end of last year, are the first in a series of policies expected to be unveiled in the coming months that Beijing says are intended to strengthen cybersecurity in critical Chinese industries. As copies have spread in the past month, the regulations have heightened concern among foreign companies that the authorities are trying to force them out of one of the largest and fastest-growing markets.

In a letter sent Wednesday to a top-level Communist Party committee on cybersecurity, led by President Xi Jinping, foreign business groups objected to the new policies and complained that they amounted to protectionism.

The groups, which include the U.S. Chamber of Commerce, called for “urgent discussion and dialogue” about what they said was a “growing trend” toward policies that cite cybersecurity in requiring companies to use only technology products and services that are developed and controlled by Chinese companies.