BEIJING (AP) _ Trying to tighten its hold on the fast-moving Internet, China is ordering companies to register software used to transmit sensitive data and threatening punishment for letting government secrets slip onto the Web.

The moves, set out in regulations, could scare off foreign firms eager to tap China's bursting Internet market and retard electronic commerce in its infancy. They also underscore the Chinese leadership's ambivalent desire to exploit the Internet for business while constricting information considered threatening to communist rule.

``It's like saying you want to develop railroads and then throwing down a different gauge track not used anywhere else in the world,'' said William Soileau, an information technology lawyer with Denton Hall in Beijing.

Rules announced Wednesday formally extend China's vague state secrets law to the Internet. Everyone, from Internet servers to chat-room users, must gain approval from agencies protecting government secrets before publishing previously unreleased information on the Web, according to the States Secrecy Bureau regulations released in People's Daily.

Perhaps most chilling for business are regulations ordering companies and individuals to register with the government by Monday the software used to protect transfers of sensitive information. Forms require companies to hand over the serial numbers and list the employees using the software, possibly making it easier for the government to track use.

So-called encryption software is used to prevent prying into everything from electronic mail to banking settlements. Popular products like Netscape browsers contain encryption software, as do some Microsoft products.

``This can potentially compromise the trade secrets of companies,'' said Jay Hu of the United States Information Technology Office, an industry lobbying group.

Hu said China was worried that foreign encryption technology might contain secret pathways enabling outsiders to peer into Chinese businesses or government agencies.

The clampdown also highlights government fears about the use of encrypted communications by political dissidents and the banned Falun Gong spiritual movement. Falun Gong followers have used e-mail and the Internet to meet and hold protests in defiance of a six-month ban.

Chinese Web sites have displayed a liveliness unfound in the traditional and wholly state-controlled media. In recent months, Web sites have carried reports on tests of a new submarine-launched missile and a sprawling corruption scandal that has threatened to ensnare a senior party leader _ both unreported by official media.

That lack of restraint comes despite repeated government regulations meant to bring the Internet under control. China has set up a special police force to monitor the Internet and has in criminal trials accused political dissidents and leaders of Falun Gong of disseminating anti-government views and state secrets on the Web.

Still, Internet use soars. Official media reported that in the last six months of 1999, users more than doubled from 4 million to 8.9 million.