China wants people who buy new cell phone numbers to register their personal details, joining many European and Asian countries in curbing the anonymous use of mobile technology.

Most countries that have such rules say they prevent the use of unregistered phones in terror attacks or drug crimes. In China, authorities say they have their sights on rampant junk messages — but some believe the move gives the government a new tool for monitoring its citizens.

The regulation was “the latest campaign by the government to curb the global scourge of spam, pornographic messages and fraud on cellular phones,” the China Daily newspaper reported. The rules that started Wednesday apply to everyone, including foreigners on short visits.

Similar rules have been implemented in several Asian, European and Latin American countries, often after phones were used to detonate bombs, organize terrorist attacks or conduct criminal activities. Federal legislation has been introduced in the United States, where prepaid phones have long been used by drug dealers. In many places, however, the rules are easily skirted with fake IDs or false names.

But human rights advocates say China might be looking for a way to track people who spontaneously join protests. Users could previously buy low-cost mobile phone SIM cards anonymously with cash at convenience stores and newspaper stands and use them right away.

“I think the government has an eye on Iran where protests were fueled by text messages and Twitter and they are doing this for social stability reasons,” said Wang Songlian, research coordinator with the Hong Kong-based Chinese Human Rights Defenders.

She added that the new requirement fits a pattern of tightening government control over new communication technologies.

China censors Internet content it deems politically sensitive and blocks many websites, including Twitter, Facebook and YouTube. Following ethnic riots in far western China’s Xinjiang region, international phone service and the Internet in the region were suspended for months.

The new regulation probably won’t impact Chinese dissidents, many of whom already have their phones closely monitored, but it could help police track down ordinary people who take part in protests, Wang said. China has seen a growing number of protests sparked by labor disagreements, anger over pollution or other issues.

The ID requirement is also raising new privacy concerns and will likely upset some customers unwilling to give personal information to vendors and telecom companies for fear it will be resold, said Duncan Clark, managing director of BDA China Ltd., a technology market research firm.

China has more than 800 million mobile phone numbers already in use. The Global Times newspaper reported Wednesday that about 320 million of those were purchased without real-name registration. They will have to be reregistered by 2013 or could be suspended, it said.

China Unicom, one of the country’s three major state-owned phone carriers, issued a notice on its website on Aug. 20 saying that the Ministry of Industry and Information Technology had informed them that real-name registration would be required for all new telephone number purchases starting Sept. 1.

China Mobile — the world’s biggest phone carrier by subscribers — was also complying with the directive, said a customer service representative who would only give his surname, Zhang.

The Ministry of Industry and Information Technology did not respond to questions about the new rules and a man who answered the phone at the ministry’s press office refused to comment.

At a newspaper stand in downtown Beijing where SIM cards are sold, a 24-year-old officer worker said she read about the new regulations Wednesday morning on her mobile phone and supports the move.

“I hope it will help crack down on spam,” Wu Xi said. “It won’t be a problem if I have to show my ID.”

Chen Haimin, the owner of a Beijing convenience store, said he was still selling cards without personal information and he was doubtful that the new scheme would put an end to junk mail.

“How do you know if people are even showing their real ID?” he said. “People who want to send spam can always come up with ideas to get around the regulations. Besides, it’s not hard to get a fake ID.”