The social media network that has more than 500 million users worldwide, said in a tweet that its policy does not permit the use of Twitter to promote terrorism, Xinhua reported.
Twitter, compared with other US-based networks of its kind, has been considered to be more reluctant to intervene against contents posted by users.
In its history of nearly 10 years, it has had a system in place against child pornography.
According to a report released in 2015 by Brookings Institution, a Washington DC-based think tank, the IS had at least 46,000 active Twitter accounts over a three-month period in 2014.
The pressure for Twitter to curb propaganda by the IS and other extremist groups comes from the US government as well as non-government groups and individuals. Last month, it was sued by the widow of a US national killed in an attack on a Jordanian police training centre.
The plaintiff alleged that Twitter makes it easy for the IS to promote violence.
However, Twitter said on Friday it has “always sought to strike a balance between the enforcement of our own Twitter Rules covering prohibited behaviours, the legitimate needs of law enforcement, and the ability of users to share their views freely – including views that some people may disagree with or find offensive.”
Meanwhile, the network said it has increased the size of the teams that review terrorism-related reports, so as to reduce its response time.