Beijing police have detained more than 30,000 people in the past three years in crackdowns against Internet crime.

The Beijing Public Security Bureau has launched several campaigns since 2011, targeting online offenses, maintaining cyber security and cleaning up the Internet environment, according to a statement on Wednesday.

Last year, the police in the capital arrested more than 23,000 people on suspicion of Internet crimes, six times the number in 2011, the authority said.

More than 70 percent of China's large Internet companies are now based in Beijing, and more than 900,000 websites have been registered in the city, according to the police. This concentration of Internet-related activity is a major reason for the increased frequency of online crimes.

To alleviate the rapidly rising number of Internet-related offenses, the bureau set up an office to improve the city's cyber security in 2011, and it began cracking down on rumor dissemination, human trafficking, gun purchases and online fraud.

In April, Beijing Chaoyang District People's Court sentenced Qin Zhihui, better known by his online alias, Qin Huohuo, to three years in prison for defamation and causing trouble, the first case in which someone was punished after damaging the reputation of celebrities by spreading rumors.

In August, another former popular micro-blogger, Yang Xiuyu, known as Lier Chaisi, also stood trial in the court for illegal business operations after he benefited from publishing online rumors and helping companies delete negative posts.

In January, the city's police started investigating people who disseminated terrorism information, arresting more than 50 suspects and seizing 728 related online products, such as videos and books.

Wang Qi, a police officer of Huaqingyuan community's police station in the city's Haidian district, said that cracking down on online offenses is now a major part of his work.

"The online security office under the district's sub-bureau sometimes gives us information that someone is spreading online rumors in an Internet bar and helps us to fix the suspect's location so that we can make an arrest," Wang said.

He confirmed that many crimes committed in traditional ways have shifted to the Internet in recent years, adding to the challenge of investigation.

The bureau selected more than 400 police officers from across the city last year, and increased IT knowledge in each police station, to target Internet-related crimes, he said.

In September, Wang delivered brochures on preventing online fraud to colleges under his jurisdiction and dispatched officers to banks to keep elderly residents from being cheated.

"We also contacted the big Internet companies, including Sina and Sohu, guiding them to tackle online offenses at the time they occur," he added.

Criminal lawyer Liu Honghui said the crackdown on online crime needed to be extended nationwide and not be confined solely to the big cities.

"The Internet training should cover all police, irrespective of age, rank or location," he said.

Liu also called for the wider promotion of real-name registration for online shopping and dating services.

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