Twitter users in China are facing threats, lengthy interrogations and even days in a detention center after posting messages critical of the Chinese government, according to a report by The New York Times.

The social media crackdown is reportedly part of President Xi Jinping's campaign to censor what's posted online in the country. 

The Times interviewed nine Twitter users who were questioned by the police and reviewed a recording of a four-hour interrogation. At one point, Chinese police questioned a Twitter user, who was chained to a chair, for eight hours. Another spent 15 days in a detention center, according to the report. 

Users told The Times that police would print out tweets critical of the government and ask them to delete them or their accounts. 

Huang Chengcheng, the activist who was interrogated for eight hours, told the news outlet he signed a promise to stay off Twitter after being held by police. 

Twitter is currently banned in China, but people in the country use software to access the social network. Roughly 3.2 million people use Twitter in China, according to an estimate based on a survey of 1,627 Chinese internet users last year by Daniela Stockmann, a professor at the Hertie School of Governance in Germany. That's only about 0.4 percent of China's Internet users. Still, as The Times notes, the social network fuels political debate and discussion in the country. 

Twitter declined to comment. The Chinese embassy did not immediately respond to a request for comment. 

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