Twitter said it already has rules to discourage this activity.
Twitter has suspended over 125,000 accounts, most of them linked to the ISIS group, as part of a stepped-up effort to crack down on "terrorist content" on the messaging platform, it said Friday.
The accounts frozen since mid-2015 were targeted "for threatening or promoting terrorist acts," said Twitter, which is under pressure from governments to act.
"Like most people around the world, we are horrified by the atrocities perpetrated by extremist groups," Twitter said on its policy blog.
"We condemn the use of Twitter to promote terrorism and the Twitter rules make it clear that this type of behavior, or any violent threat, is not permitted on our service."
The announcement comes after the United States and other governments urged social networks to take more aggressive steps to root out activity aimed at recruiting and planning violent acts.
Twitter said it already has rules to discourage this activity but that it was driving up enforcement by boosting staff and using technology to filter violence-promoting content. But it warned there is no easy technological solution.
"As many experts and other companies have noted, there is no 'magic algorithm' for identifying terrorist content on the Internet, so global online platforms are forced to make challenging judgment calls based on very limited information and guidance," Twitter said.
"In spite of these challenges we will continue to aggressively enforce our rules in this area and engage with authorities and other relevant organizations to find viable solutions to eradicate terrorist content from the Internet and promote powerful counter-speech narratives."