Facebook Inc will start warning some users that they may have seen extremist content, Reuters reported.

Screenshots shared on Twitter showed a notice asking "Are you concerned that someone you know is becoming an extremist?" and another that alerted users "you may have been exposed to harmful extremist content recently." Both included links to "get support."

Facebook said a small test, which runs only on its main platform, has been launched in the United States as a pilot for a global approach to preventing radicalization on social media.

"This test is part of our larger work to assess ways to provide resources and support to people on Facebook who may have engaged with or were exposed to extremist content, or may know someone who is at risk," said a Facebook spokesperson in an emailed statement. "We are partnering with NGOs and academic experts in this space and hope to have more to share in the future."