Chinese authorities have launched a campaign to "eliminate" malpractice on instant messaging services.
They allege that some people have used such services "to distribute illegal and harmful information, seriously undermining public interests".
China has said suspects arrested in recent anti-terror sweeps shared their knowledge of making explosives via chat services and text messages.
Instant messaging apps have become hugely popular in China.
One of the biggest ones, WeChat, boasts more than 800 million users.
Over the past few years social media platforms have gained popularity among Chinese internet users keen to voice their opinions and share unfiltered information.
China even introduced a law to allow the government to imprison micro bloggers, and dozens were arrested last year.
Subsequently, many users have ditched social media platforms in favour of mobile messaging services.
China's state-owned media agency, Xinhua, reported that the latest campaign will "target public accounts on instant messaging services, which can spread information on a large scale and mobilize followers".
It will crack down on those spreading rumours and information relating to violence, terrorism and pornography.
Those using instant messaging services for fraud will also be targeted.
"We will firmly fight against infiltration from hostile forces at home and abroad," Xinhua quoted China's state internet information office as saying.
Seven firms offering instant messaging services, including WeChat, Momo, Mi Talk and Yixin, have agreed to cooperate with the authorities and launch internal inspections, Xinhua said.