The lawsuit allegedly seeks monetary compensation "in amounts to be determined at trial" for the plaintiffs, who argue that Twitter "has violated, and is continuing to violate, the [US] Anti-Terrorism Act."
The lawsuit was reportedly filed by the families of New York siblings Sascha and Alexander Pinczowski, who were killed in a metro bombing claimed by ISIS in Brussels last March, and of Nohemi Gonzalez - an American student killed by ISIS in Paris in the November 2015 attack that claimed the lives of at least 130 people.
The text of the legal document charges that the social media company played "a uniquely essential role in the development of ISIS’s image, its success in recruiting members from around the world, and its ability to carry out attacks and intimidate its enemies."
The legal document further accuses Twitter of "having knowingly provided material support and resources to ISIS."
Business Insider reported that Twitter has not yet responded to a request for comment on the case.
In December, Twitter, along with social media giants Facebook and YouTube, announced that they were taking steps to combat the spread of online terrorist content.
According to the companies, they are working to create a shared industry database of “hashes,” unique digital “fingerprints,” for violent terrorist imagery, terrorist recruitment videos or images that have been removed from their services that they will then share with one another.