Twitter has suspended over 125,000 accounts for threatening or promoting terrorist acts since mid-2015, the social media site announced Friday.

The sites were primarily related to Islamic State, Twitter explained, in a blog post. “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,” it said. “As the nature of the terrorist threat has changed, so has our ongoing work in this area.”

Related: Widow sues Twitter over ISIS' 'unfettered ability' to use platform

ISIS is adept at using social media, including Twitter, as a propaganda and recruitment tool.

In its blog post, Twitter explained that it has also increased the size of the teams that review reports, significantly reducing its response time. “We also look into other accounts similar to those reported and leverage proprietary spam-fighting tools to surface other potentially violating accounts for review by our agents,” it said. “We have already seen results, including an increase in account suspensions and this type of activity shifting off of Twitter.”

The social media firm also highlighted its cooperation with law enforcement, when appropriate, citing comments made by FBI Director James Comey last year recognizing Twitter’s commitment to blocking terrorist content.

Related: ISIS supporters may operate over 46,000 Twitter accounts, study says

Additionally, Twitter said that it partners with organizations working to counter extremist content online.

A study released by the Brookings Institution in March 2015 warned that ISIS supporters may be operating more than 46,000 Twitter accounts. The study found that almost one in five ISIS supporters selected English as their primary language when using Twitter. Three quarters selected Arabic.

Twitter has come under fire for its handling of extremist groups’ accounts. Citing ISIS’ "unfettered ability to maintain official Twitter accounts," the widow of an American killed last year in an attack at a police training center in Jordan has sued the social media company for allowing the group to spread its message.

The San Francisco-based company called the lawsuit meritless, but said it was “deeply saddened to hear of this family’s terrible loss.”