The Chinese Ministry of Public Security (MPS) arrested 15,000 people for cybercrimes as part of a long-term operation dubbed “Cleaning the Internet,” Reuters reported.

The arrests stemmed from about 7,400 specific incidents spread over 66,000 websites that were investigated, but the MPS did not say exactly when the arrests took place. The operation launched last month and is expected to go on for a total of six months.

The MPS said those targeted were putting “illegal and harmful information” online, in addition to ads for pornography, explosive and gambling.

The MPS is part of the State Council, China's chief administrative body and principal police and security authority. The Chinese government has greatly increased pressure on what can appear on the internet inside the country since 2013 when Chinese President Xi Jinping came to office.