Residents in the Tibetan capital of Lhasa will soon have to register their names if they want to make photocopies, in an apparent government bid to deter separatists from printing pamphlets.

The Chinese government has carried out a sustained crackdown on alleged separatist activity in Tibet and its surrounding areas following anti-government protests in 2008 that erupted in violence. The riots sparked sympathy protests in Tibetan communities across a quarter of west China _ the widest uprising against Chinese rule in a half-century.

An official with the Lhasa Public Security Bureau said Wednesday that the local government hoped to begin enforcing the registration rule soon but he couldn't give an exact launch date.

"Since May 1, Lhasa's public security forces have been investigating these (photocopying) businesses and keeping track of them," said the official, who would only give his surname as Ma. "There's a lot of work to be done before we actually take this measure."

He refused to specify what sort of printed material police were concerned about. The official China Daily newspaper reported Wednesday that police were worried that separatists were using pamphlets to spread illegal content.

China says Tibet has always been part of its territory, but many Tibetans say the Himalayan region was virtually independent for centuries until Chinese troops invaded in the 1950s.

Beijing blames the exiled Tibetan spiritual leader, the Dalai Lama, for fanning anti-government sentiment and routinely purges monasteries and nunneries, where support for the Dalai Lama and Tibetan independence run high.

Since the 2008 riots, Tibetan protests have continued to occur sporadically in heavily Tibetan regions. In China's far western province of Gansu on Saturday, 15 Tibetans were wounded in a clash with local police after they blocked a road leading to a cement factory they blame for spewing pollution, an overseas Tibetan rights group said.

The International Campaign for Tibet quoted an exiled Tibetan in touch with locals in Gansu's Xiahe county as saying 15 people were hospitalized with gunshot wounds or injuries from beatings by police. The Tibetans were upset because ash from the factory was polluting their grazing land and construction was encroaching on a religious site, the statement said, citing a petition prepared by the protesters.

The China Daily said the new rules for copy shops in Lhasa would require customers to submit both their names and addresses. Only permanent Lhasa residents or people with temporary Lhasa residence permits would be allowed to make copies, it said.

An employee of the Yongkang Photocopying and Printing Shop in Lhasa said by telephone that he had yet to receive any notice on registering customers. He said though that the shop already refuses service to some people based on what they are printing.

"If any material is written in characters we don't know, like Tibetan, then we don't print them," said the man who would give only his surname, Luo. "There's no official notice on that, but we just want to be safe."

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Associated Press researcher Zhao Liang contributed to this report.