Sina Weibo's content moderators block about 140,000 comments a day because they contain either libelous or threatening language, a senior executive has revealed.

"Users who break the rules 50 times have their account suspended for 60 days, and their name is added to list shared on our platform," Cao Zenghui, vice-president of Sina Weibo, said on Tuesday.

He was speaking at a forum in Shanghai to discuss how to prevent cyberspace from being polluted by harmful information.

The event was part of the annual Cybersecurity Week, which runs until Sunday and aims to raise awareness about cybersecurity and related policies.

China had 751 million internet users as of June, according to Zhang Xunhong, director of the Cyberspace Administration of China's Online Communities Bureau.

President Xi Jinping has stressed that cyberspace is the spiritual home of millions of people, and each netizen is a cell in cyberspace," he said. "As long as the quality and morality are enhanced, the foundation of cyberspace will remain healthy."

Jiang Xun, director of the Shanghai Cyberspace Administration, said the internet has brought many advantages, but also has raised the risk of fraud, and made it easier to spread rumors and other illicit content, such as pornography.

"It's the common aspiration of society to establish a safe and clean cyberspace," he added.