A year-long campaign by the Hu Jintao government to silence unofficial voices in China and to assert control over independent expression continues with an order this week for all Chinese websites and bloggers to register their real names with authorities, or be closed by June 30.

Tens of thousands of Chinese use cyberspace to publish views on subjects ranging from politics to relationships, and have been able to avoid official censure by writing anonymously. But now Internet activity will be monitored in real time by Information Ministry computers. Sites and users not registered may be arrested.

Official efforts to police cyberspace here comes amid a host of new measures and events that underscore a broad tightening of controls by the central government. A senior Chinese diplomat posted to Australia is seeking asylum in a hotly debated espionage case now underway in Sydney.